Play.com have this Sony Ericsson MBS-100 Portable Bluetooth Speaker for £27.99. It's pretty stylish. I saw one in the Sony Ericsson shop in Kensington High Street (priced a tiny bit higher than this, hehe) and they really are very nice.
As always, this is the cheapest price that I could find. If you have any comments, reviews, cheaper prices, etc, then please post a comment and let us know what you have to say!!