james.php

<?php
	
	$context = Timber::get_context();
	$context['work'] = Timber::get_posts('post_type=work&numberposts=25');
	$context['posts'] = Timber::get_posts();
	Timber::render('index.twig', $context);

The idea is to avoid automatic in favor of explicit (and hopefully, brief). Your index.twig might look like this:

<section id="posts">
{% for post in posts %}
      {% include "tease-post.twig" %}
{% endfor %}
</section>

<section id="work">
{% for work_item in work %}
     {% include 'tease-work.twig' with {post:work_item} %}
{% endfor %}
</section>

Sorry to take so much of your time.
I have this sort of working but it is still putting both of these on the same page
(and another issue where it cannot find any of the 'work' posts.

is the upstatement site set up in a way that would work? would it be easier for me to go through those files rather than asking you questions left and right?