I do a little home anodising when the weather is suitable (ambient temps) but for proper 'hard' anodising you're going to need a specialist company. Google your local area & I can guarantee there'll be at least 5 or more . . . isn't Banbury in the F1 triangle?

You're going to have to phone 'em up & find one which doesn't have a minimum invoice charge (my regular charges £50min).

P.S. Spin 'em it's a prototype that you're considering for manufacture & 1 or 2 might even offer to do the job as a freebie :-)