yeah hitchin a ride rules lol, im assuming the UK release will actually come already with the update, it would be stupid of SCEE to release it then release the update, they may as well do it before hand, depends if they where already manufactured before the release came out.
if the update isnt on already the US Update should work on it, the jap update came out before the US update and The Jap Update worked On My US PSP. you risk though, don't blame me if it doesnt work.
http://psp.ign.com/articles/644/644823p1.html
the download link is on that page, keep the link for when you get your psp just incase it hasnt got the update, and in the meantime read the article, lets you knw whats on the update anyways.