I think DesmoDuke had some done the most recently - last couple of years or so. Yes - that one! "I've used Langcourt a couple of times, quick turn around and quality was spot-on." (DukeDesmo)
You don't say what sort of barrel, nor for what model. A few months ago I had a Pantah barrel rebored and Nikasil coated by Langcourt of Weston Super Mare. They were very good. Is that the sort of thing you need?
St3 is a nikasil type barrel, and as said langcourt is as good start but not the best, I think it is the only option in the uk though.
Langcourt & BLR, cheers gents. Sev - That will take the motor out to 1098cc I think (98mm Pistons from a 996) but the motor is 3 valve, not for HP but for the torque should take it to high eighty low nineties. BBBBBBBBBBBBBBBBBAAAAAAARRRRRRRRRRRRRRRRRRRRPPPPP!!!!!
If you get them Nikasil coated, be very careful if you should happen to fit chrome rings as well..........'Running in' is a must. AL