I have a Jap PSP with 1.5 firmware, and so can't run all of the UK UMD movies (some require a more up to date firmware, and there's no way i'm losing my SNES emulator so i can have a slightly better version of Transformers!). To my knowledge theres no way of knowing without putting one in your PSP and having a go.
This thread is just for people to list which ones they've found definitly DO work, and which ones DONT. Should save us all some time (unless someone knows of a comprehensive list already - I had a search around and couldn't find one).
So far all i know of these 3,
TransFormers:The Movie and Saw DON'T work
Bad Boys DOES work