Moment of truth. Valves in, the tape is where I had them all tested and wrote a note on them, RCD in place.
Totally works, woo. Issues are that the power switch doesn't turn off (I was turning it on from the wall, in case of exploding), and there is still some noise from the pots an hiss, occasional crackle, but loads quieter than the last one I had. Some new resistors in the pre should sort that. New switch is fairly important too.