Make your own - I did! Cost me less than a fiver.
I bought a blue socket from ebay for a couple of quid (
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=250354482996) and then a UK socket from maplin or B&Q (
http://www.maplin.co.uk/Module.aspx?ModuleNo=13134) for about the same. Put an old piece of 3-core flex between the two and you're sorted.
You can then plug in a 4-way extension or similar to power you uk plugs - I picked a few up from the pound shop of all places! Everywhere else charge over a fiver for them.
If you want to save a couple of quid, wire the blue plug straight onto the 4-way extension instead!