[thejazzageuk]

Thanks Techman. I'm always happy to follow advice- and in the past yours has been spot on. I started with some static checks, all with set unplugged.
ONE: At first the primary winding check revealed infinite resistance between L and N. However I shored out the OFF/ON switch and then got a reading of 8.8 ohms (a bit low?). Removing the switch short the reading was a couple of hundred ohms eventually going down to 47 ohms with switch on. I guess the initial high readings could be due to oxidizing of switch contacts?
TWO: I then tried to get the heater resistance- from the V8-triode phase splitter valve socket (L63) it read 0.4 ohms between pins 2 and 7 heater.
THREE: Finally- to check high voltage 2ndry winding, I removed V11 rectifier and measured 180 ohms between pins 4 and 6 .
Do these seem reasonable?
My next step was to replace a few (the minimum) of components, as like you suggest I am reluctant to cut it about more that necessary. The ones I looked at and thought of changing are shown in the attached photo and listed below, but would be very grateful if you can advise it this is sensible.
C39 -0.01 paper cap- coupling for V7. REPLACE?
C40/41 caps for Tone control. LEAVE?
C37 0.5 signal valve screen voltage cap. REPLACE?
C35 signal coupling cap 0.5 REPLACE?
C45 abd C46 coupling caps 0.25 for V9 and V10. REPLACE?
C51/52 mains filter caps. REPLACE?