Here in the State's we have Radio Shack's and they sale the "generic" adapter. You need a store that carries all those little electronic doodads like circuits (not Cricut)

, replacement parts for electronic equipment, etc... They should have your adapter. I don't know what the specs are on the adapter for the UK Cricut. I do have the USA Cricut specs if it helps.
The USA adapter is:
Switch Mode Power Supply
Model: KSH1800250T1M2
Input: 100-240V~50/60Hz 1.2A
Output: 18V 2.5A 45W
I just took a peek for you. You all do have Radio Shack's. Here's a link:
http://www.radioshackuk.co.uk/