I have just spent a pleasant morning with Dave Lunt and can confirm he is still very much firing on all cylinders. With me doing the heavy lifting, he gave my 1981 SVT a quick service, tested all the valves, replacing three of the preamp ones which were a bit noisy, and tweaked the bias settings to get rid of most of the hum.
He's based in Macclesfield, Cheshire and I would heartily recommend him with the caveat that you might need to pitch in and help if your amp weighs 3 tons like mine!