Ok regulators are shot, caps are shot, half the diodes are shot in the power supply.
So I bypassed the power supply, which is neatly possible due to two links on the board, and chucked a bench power supply on it.
And you know what? It only still works perfectly. I am extremely surprised!
It pulls a monster current of 40mA per rail and the supply appears not to require tracking so I'll just knock up a LM317/337 type supply, stick and IEC socket and fuse holder on and rip the old ICs and caps out. Phew!