Just wrote this code which totally worked beyond my imagination before realising I no longer needed to use Variations on this particular WooCommerce site. So, might as well share it.
Insert this into your-theme/woocommerce/single-product/product-image.php
This will output each variation’s thumbnail and name. With some jQuery to update the variation drop-down to match the thumbnail you click.
Now you’ll need to change some of the variables in there. Change select[name=”attribute_colour”] to match the variation drop-down you’re targeting.
I probably could’ve improved this to popular the drop-down name automatically…