Be sure to hit some of the bike shops there - they'll have some stuff you've not seen in the US before.
But as far as any deals go - forget it. In the Uk, for example, they pay in pounds what we pay in dollars. For example, a helmet here might cost $300 while it costs 30o pound sthere. A pound equals around $1.60 to $1.75. So if you bought it there with American dollars, it'd cost you $480+.
This isn't true with everything, but not too far off on a lot of stuff either. Anythiung that you can buy in the USA will definitely be a lot cheaper.
Having said that, there's lots of cool UK made stuff that you just can't get here as easily: crowtree leathers, BK leathers and some others. It's worth having a look at those while you're there.
Rent a bike while you're there - you can rent just about anything as fare as bikes go - even R6's. Not like the USA where you can only rent HD, BMW and Gold Wings.