They aren't THAT difficult to work on if you are methodical, there is a good guide on the web somewhere by that chap in Spain who posts on here. Probably just needs a strip, a clean, relube and Bobs your whatnot.
If you don't want to do it then I think City Air Weapons in Solihull is a good place to take it.
For help, advice or sales, our contact details are:
CITY AIR WEAPONS
247 LYNDON ROAD,
OLTON,
SOLIHULL,
WEST MIDLANDS B92 7QP
UNITED KINGDOM
Telephone/FAX: +44 (0) 121 742 1329
Shop opening times: Thursday, Friday & Saturday: 10:00 - 17:30 (other times by appointment)
Email Addresses:
Orders or Enquires: sales@.com
Help or Advice: advice@.com
If you want rid, then I know someone who would be interested!