Looking for reliable source to fix a BYOC Large Beaver in England...

[loopyloop]

Hi guys!
Can anyone recommend someone who fixes guitar effects in England?
Built a BYOC Large Beaver but doesn't sound quite right (i.e effect is weak, bit of noise) and don't have the time or passion to mess with it.

Doesn't have to be a business as such, private individual would be fine, but needs to be reliable and not charge a fortune...
Thanks.