Spoke to a guy called Mervin at Mansfield Anodisers yesterday... minimum order of £20 per colour although this doesn't include pollishing.
I asked him about a set of bar ends (Stubbie Pros), Cranks (Topline SLS), Brake levers (987s) and a few other bits.
I wanted two colours and he quoted me circa £50 but caveated that the finish is largely dependent on the material - stuff thats already been anodised is generally OK, and billet machined works better than cast. The polishing can be the expensive bit, depending on the complexity of the part involved.
Basically he said about £50 and to send him the parts. He'd then assess each one and call with an exact price before doing any work or incurring any charge...
As far as what consitutes the £20 minumum order, he couldn't define. I just listed the parts I wanted done and he quoted.
Hope this info is useful.