Just lots of playfield globes had died - no reason it would seem (put it down to moving). Replacements all work, although to get a couple in required removing boards from the underside of the playfield. And one globe holder came loose after I tried to force a globe in there, so did a hack solder job on that one to get it going (really the holder needs replacing). The playfield looks grouse with all the lights working again.
While I was under the playfield I removed the tunnel between the trapdoor and the gun popper (which houses the gun lock switch - a rollover). I mentioned earlier I started having intermittent gun popper problems, which I rectified earlier by resoldering the positive to the solenoid. Well, at some point since then the ball wasn't getting to the gun popper, just sitting in this tunnel. Removal of the tunnel tonight made everything clear - the rollover switch was sitting above the switch gap and catching on the tunnel floor, jamming the ball in the tunnel. With some judicious bending the switch is now behaving itself and the trapdoor -> gun popper is operating really well.
I love this stuff; I can see why people get hooked on it. Now someone needs to donate me a project pin. Might keep on eye on the local paper garage sales.