The valve lineup should be sufficient and easier to define. In those days there was a fairly standard mullard design for most receivers. The big advantage being the simplicity of getting parts and also fault finding tended to be a doddle. The model number should be traceable, but the "standardisation" rendered a trawl of manuals unneccessary.
Not sure why the bloke posted in the first place, if he has not got any abilities with a DMM, or there is no direct link to Brexit then it isn't really DIY.
The work involved getting the unit up to a reasonable standard of quality and reliability after the main repair would obviously be beyond him also.
I am not convinced that a radio amateurs club is the right approach either. Thanks to the RSGB most amateurs just open boxes and get the nice man at the shop to solder their PL259's on.
Proper amateur radio died off in the 70's.
Frankly I feel sorry for the bloke, when I read some of the garbage that passes for advice, I do tend to wonder what the reasons are for spewing forth such drivel. The genius suggesting that flashover was a serious risk in what has to be a class A output stage of an absolute maximum of 3W is to be complemented. That is truly Edinburgh Fringe stuff.
AB