JSON United Kingdom Counties with Abbreviation and Country

uk-counties.json

[
    {
        "name":"Avon",
        "abbreviation":"AVN",
        "country":"England"
    },
    {
        "name":"Bedfordshire",
        "abbreviation":"BDF",
        "country":"England"
    },
    {
        "name":"Berkshire",
        "abbreviation":"BRK",
        "country":"England"
    },
    {
        "name":"Buckinghamshire",
        "abbreviation":"BKM",
        "country":"England"
    },
    {
        "name":"Cambridgeshire",
        "abbreviation":"CAM",
        "country":"England"
    },
    {
        "name":"Cheshire",
        "abbreviation":"CHS",
        "country":"England"
    },
    {
        "name":"Cleveland",
        "abbreviation":"CLV",
        "country":"England"
    },
    {
        "name":"Cornwall",
        "abbreviation":"CON",
        "country":"England"
    },
    {
        "name":"Cumbria",
        "abbreviation":"CMA",
        "country":"England"
    },
    {
        "name":"Derbyshire",
        "abbreviation":"DBY",
        "country":"England"
    },
    {
        "name":"Devon",
        "abbreviation":"DEV",
        "country":"England"
    },
    {
        "name":"Dorset",
        "abbreviation":"DOR",
        "country":"England"
    },
    {
        "name":"Durham",
        "abbreviation":"DUR",
        "country":"England"
    },
    {
        "name":"East Sussex",
        "abbreviation":"SXE",
        "country":"England"
    },
    {
        "name":"Essex",
        "abbreviation":"ESS",
        "country":"England"
    },
    {
        "name":"Gloucestershire",
        "abbreviation":"GLS",
        "country":"England"
    },
    {
        "name":"Hampshire",
        "abbreviation":"HAM",
        "country":"England"
    },
    {
        "name":"Herefordshire",
        "abbreviation":"HEF",
        "country":"England"
    },
    {
        "name":"Hertfordshire",
        "abbreviation":"HRT",
        "country":"England"
    },
    {
        "name":"Isle of Wight",
        "abbreviation":"IOW",
        "country":"England"
    },
    {
        "name":"Kent",
        "abbreviation":"KEN",
        "country":"England"
    },
    {
        "name":"Lancashire",
        "abbreviation":"LAN",
        "country":"England"
    },
    {
        "name":"Leicestershire",
        "abbreviation":"LEI",
        "country":"England"
    },
    {
        "name":"Lincolnshire",
        "abbreviation":"LIN",
        "country":"England"
    },
    {
        "name":"London",
        "abbreviation":"LDN",
        "country":"England"
    },
    {
        "name":"Merseyside",
        "abbreviation":"MSY",
        "country":"England"
    },
    {
        "name":"Norfolk",
        "abbreviation":"NFK",
        "country":"England"
    },
    {
        "name":"Northamptonshire",
        "abbreviation":"NTH",
        "country":"England"
    },
    {
        "name":"Northumberland",
        "abbreviation":"NBL",
        "country":"England"
    },
    {
        "name":"North Yorkshire",
        "abbreviation":"NYK",
        "country":"England"
    },
    {
        "name":"Nottinghamshire",
        "abbreviation":"NTT",
        "country":"England"
    },
    {
        "name":"Oxfordshire",
        "abbreviation":"OXF",
        "country":"England"
    },
    {
        "name":"Rutland",
        "abbreviation":"RUT",
        "country":"England"
    },
    {
        "name":"Shropshire",
        "abbreviation":"SAL",
        "country":"England"
    },
    {
        "name":"Somerset",
        "abbreviation":"SOM",
        "country":"England"
    },
    {
        "name":"South Yorkshire",
        "abbreviation":"SYK",
        "country":"England"
    },
    {
        "name":"Staffordshire",
        "abbreviation":"STS",
        "country":"England"
    },
    {
        "name":"Suffolk",
        "abbreviation":"SFK",
        "country":"England"
    },
    {
        "name":"Surrey",
        "abbreviation":"SRY",
        "country":"England"
    },
    {
        "name":"Tyne and Wear",
        "abbreviation":"TWR",
        "country":"England"
    },
    {
        "name":"Warwickshire",
        "abbreviation":"WAR",
        "country":"England"
    },
    {
        "name":"West Midlands",
        "abbreviation":"WMD",
        "country":"England"
    },
    {
        "name":"West Sussex",
        "abbreviation":"SXW",
        "country":"England"
    },
    {
        "name":"West Yorkshire",
        "abbreviation":"WYK",
        "country":"England"
    },
    {
        "name":"Wiltshire",
        "abbreviation":"WIL",
        "country":"England"
    },
    {
        "name":"Worcestershire",
        "abbreviation":"WOR",
        "country":"England"
    },
    {
        "name":"Clwyd",
        "abbreviation":"CWD",
        "country":"Wales"
    },
    {
        "name":"Dyfed",
        "abbreviation":"DFD",
        "country":"Wales"
    },
    {
        "name":"Gwent",
        "abbreviation":"GNT",
        "country":"Wales"
    },
    {
        "name":"Gwynedd",
        "abbreviation":"GWN",
        "country":"Wales"
    },
    {
        "name":"Mid Glamorgan",
        "abbreviation":"MGM",
        "country":"Wales"
    },
    {
        "name":"Powys",
        "abbreviation":"POW",
        "country":"Wales"
    },
    {
        "name":"South Glamorgan",
        "abbreviation":"SGM",
        "country":"Wales"
    },
    {
        "name":"West Glamorgan",
        "abbreviation":"WGM",
        "country":"Wales"
    },
    {
        "name":"Aberdeenshire",
        "abbreviation":"ABD",
        "country":"Scotland"
    },
    {
        "name":"Angus",
        "abbreviation":"ANS",
        "country":"Scotland"
    },
    {
        "name":"Argyll",
        "abbreviation":"ARL",
        "country":"Scotland"
    },
    {
        "name":"Ayrshire",
        "abbreviation":"AYR",
        "country":"Scotland"
    },
    {
        "name":"Banffshire",
        "abbreviation":"BAN",
        "country":"Scotland"
    },
    {
        "name":"Berwickshire",
        "abbreviation":"BEW",
        "country":"Scotland"
    },
    {
        "name":"Bute",
        "abbreviation":"BUT",
        "country":"Scotland"
    },
    {
        "name":"Caithness",
        "abbreviation":"CAI",
        "country":"Scotland"
    },
    {
        "name":"Clackmannanshire",
        "abbreviation":"CLK",
        "country":"Scotland"
    },
    {
        "name":"Dumfriesshire",
        "abbreviation":"DGY",
        "country":"Scotland"
    },
    {
        "name":"Dunbartonshire",
        "abbreviation":"DNB",
        "country":"Scotland"
    },
    {
        "name":"East Lothian",
        "abbreviation":"ELN",
        "country":"Scotland"
    },
    {
        "name":"Fife",
        "abbreviation":"FIF",
        "country":"Scotland"
    },
    {
        "name":"Inverness-shire",
        "abbreviation":"INV",
        "country":"Scotland"
    },
    {
        "name":"Kincardineshire",
        "abbreviation":"KCD",
        "country":"Scotland"
    },
    {
        "name":"Kinross-shire",
        "abbreviation":"KRS",
        "country":"Scotland"
    },
    {
        "name":"Kirkcudbrightshire",
        "abbreviation":"KKD",
        "country":"Scotland"
    },
    {
        "name":"Lanarkshire",
        "abbreviation":"LKS",
        "country":"Scotland"
    },
    {
        "name":"Midlothian",
        "abbreviation":"MLN",
        "country":"Scotland"
    },
    {
        "name":"Moray",
        "abbreviation":"MOR",
        "country":"Scotland"
    },
    {
        "name":"Nairnshire",
        "abbreviation":"NAI",
        "country":"Scotland"
    },
    {
        "name":"Orkney",
        "abbreviation":"OKI",
        "country":"Scotland"
    },
    {
        "name":"Peeblesshire",
        "abbreviation":"PEE",
        "country":"Scotland"
    },
    {
        "name":"Perthshire",
        "abbreviation":"PER",
        "country":"Scotland"
    },
    {
        "name":"Renfrewshire",
        "abbreviation":"RFW",
        "country":"Scotland"
    },
    {
        "name":"Ross-shire",
        "abbreviation":"ROC",
        "country":"Scotland"
    },
    {
        "name":"Roxburghshire",
        "abbreviation":"ROX",
        "country":"Scotland"
    },
    {
        "name":"Selkirkshire",
        "abbreviation":"SEL",
        "country":"Scotland"
    },
    {
        "name":"Shetland",
        "abbreviation":"SHI",
        "country":"Scotland"
    },
    {
        "name":"Stirlingshire",
        "abbreviation":"STI",
        "country":"Scotland"
    },
    {
        "name":"Sutherland",
        "abbreviation":"SUT",
        "country":"Scotland"
    },
    {
        "name":"West Lothian",
        "abbreviation":"WLN",
        "country":"Scotland"
    },
    {
        "name":"Wigtownshire",
        "abbreviation":"WIG",
        "country":"Scotland"
    },
    {
        "name":"Antrim",
        "abbreviation":"ANT",
        "country":"Northern Ireland"
    },
    {
        "name":"Armagh",
        "abbreviation":"ARM",
        "country":"Northern Ireland"
    },
    {
        "name":"Down",
        "abbreviation":"DOW",
        "country":"Northern Ireland"
    },
    {
        "name":"Fermanagh",
        "abbreviation":"FER",
        "country":"Northern Ireland"
    },
    {
        "name":"Londonderry",
        "abbreviation":"LDY",
        "country":"Northern Ireland"
    },
    {
        "name":"Tyrone",
        "abbreviation":"TYR",
        "country":"Northern Ireland"
    }
]

Hmm, I fee like you're missing a few counties, for example Northern Ireland has more than 6 counties: https://github.com/deldersveld/topojson/blob/master/countries/united-kingdom/uk-counties.json

Northern Ireland only has 6 counties. The areas listed in the map above appear to be outdated local government districts.