Give AK (Alan) a call on 07956 351399 - has had lots of bits anodised & also Anacoated too for past & present bikes. We are in Surrey, so not sure if he knows anone quite so far north as you are, but can tell you all about it. Say CK said to call
I get quite a lot of bits anodized for my business, try Protech in Northampton, drop me U2U if you want contact details. They do trick stuff and bits for the car racing fraternity.
Another recommended place is Hope Technology in Lancashire (www.hopetechnology.com). They specialise in mountain bike components, but also do custom anodising. Ask for Craig Metcalf.
You can buy anodising kits from 70-odd quid and if you're thinking of tinkering or need the odd part done here and there then it makes it more cost effective.