Recapping your AB wouldn't hurt as well, those capacitors are probably way beyond the end of their design life and at least a few of the ones that are near high temperature areas are probably out of spec.
OK, so thanks again to all - cleaning up the posts on the AB and removing the gunk from the connectors did the trick.
@joshc Everything appears to work, however now on power-on there appears to be a hissing/whining, almost sounds like a kettle. Sounds like it's coming from the back, near the flyback, or even where the AB connects to the back of the CRT. It only appears to be producing this sound when the crt powers up (after the sound of the initial static). Couldn't isolate it to the speakers - could it be related to the caps, as you mentioned? Have checked all connections.
@ClassicMacintosh That's a classic symptom of "corona discharge", the high voltage finding a path to ground somewhere. It's often due to dirt/dust or cracked insulation on wires. Worst case, it can be due to the insulation inside the flyback transformer breaking down, in which case you're unfortunately on borrowed time. Try powering the machine up in a dark room with the screen brightness turned down and look for kind of a blue/purple glow to track down where it is.