It doesnt. The FAQ says there are no plans to include maps for the UK at this time.
Im looking for the same. Im using the Sony Streetmate package at the moment which is OK, and does give you a nice remote to use with the GPS as well, which I find makes my system look more "retail" rather than home made.
Id love to have CoPilot though, it looks great. Perhaps we could send em nasty messages until they sort it out.