I had a reply from the frame builders. They recon they can do it for around £50.00.
I'm thinking I will just have 2mm off the bottom and 3mm of the top to give me an extra 5mm.
Thinking about the change in the head angle: this really will be minute and in fact most of the problems are caused by the fact that the alloy headsets I've been using have a higher stack height than the orignal steel one, so are probably raising the front a couple of mm in any case.
The frame I have is very scruffy and really needs a re-painting and I've been thinking of having it powder coated for some time now. I would also like the cable routing changed to be all along the right side of the top tube and was thinking of having some new braze-ons added for this - I was thinking I could remove the old ones myself.
Head tube shortening, new braze-ons and powder coating I reckon will cost somewhere in the region of £200 to £250. My question is, is it worth it for a 1990 Pine Mountain frame, or should I perhaps look for something in better condition to start with?
On the one hand, I've owned this frame from new, I know and like how it rides and have a certain amount sentimental attachments just becuase I've had it so long. On the other hand, I keep looking at some of the lovely stuff that shows up in the Reader's MTBs section. Early 90's Kona Explosif, Ritchey, Clockwork Orange, Rocky Mountain, I really like the wishbone stays on the latter two. :?