I have a project that requires making relatively large castings (up to 1 litre in a single pour) of crystal clear epoxy that is both UV stable and can be polished to a high gloss finish. 

Certainly sounds like Poly is the way to go. My workshop is solar powered hence my hesitance re heating for long periods - a light bulb based heating box is a great idea. Like it 😀. Many thanks for all the feedback.