Happy greetings from Stuff HQ - we just updated our UK PSPs to the 2.0 firmware and it works perfectly. So far.
We already knew that the update - which adds a web browser, codec support and various other cool features that we've listed here - works on US and Japanese PSPs.
The fact that we were able to update our models suggests all UK PSPs will come preloaded with 2.0 firmware. Which means the web browsers are on Sony! Huzzah!
If you've already taken the plunge and imported a PSP, you can get the new firmware from Sony Playstation's Japanese site [Google English translation].