Mr. D of the Atomic Tangerine blog dropped this over for a service, various small misbehaving, including non working reverb and some not right sounding gain channel.
Again did that thing where I started taking apart before photoing it. Whipping out all the valves and running them through my exciting new tester explained the not working reverb, a dead half on one of the preamp valves. Power valves were all good, which is relief since those are the expensive bit to sort.
Various PCB in there, everything is mounted on them, not ideal, but they are separate and secure, so not so much flexing in various places. Do need lifting out to get a look at the components. I can see a disconnected wire from an LED (these have been replaced badly at some point) and various incomplete joints on the preamp valve PCB. Need to lift the boards for a look at the state of the caps on there next.