Thanks Julie - which gives me some hope. It did manage to pick up one station (plus lots of crackling) prior to my cleaning it in what looked like the first time since 1952. Since then no crackling but no stations. Lights up, as do all valves, and I can hear a purr from the speaker but no Clitheroe Kid or Round the Horne alas
Worth swapping those two valves around then I guess in case I did mess them up.