I've used a few repair specialists in the UK before.
Newton Ellis (http://www.newtonellis.com/
Serviced my Leica II, Canon IV SB and Canon 7 50mm 0.95 lens.
Whilst servicing my Canon 7 lens he received another one from Peter Loy for refurbishing too - meaning he was able to match them up identically for a better overall job on it. The repair technicians are friendly and have quite an extensive knowledge of vintage gear.
Luton Cameras (http://www.lutoncameras.co.uk/
Great with Olympus gear plus all work carried out comes with a six month warranty. The staff know what they are talking about and they can source rare parts with little hassle.
(They found a donor OM-3, spare parts for a OM Zuiko 40mm f/2 and Pen F camera body!)
Sover Wong (http://www.soverf2repair.webs.com/
A Nikon F2 (and F) master technician. Don't send your F2 to anyone else.
Serviced my F Black Photomic head to full working order.
I've recently contacted Miles Whitehead (http://www.mwcamerarepairs.co.uk/
) and I sent him some gear. Had a quick chat about the gear and he genuinely sounds like he knows what he's doing.
Hope this helps.