There must be a switch somewhere that is playing up.  Have you disconected the slam tilt and checked the cabinet switches?  My cabinet switch connector needs repinning (too lazy) and when it isn't in the right spot, switch 24 goes open and causes others to fail. If you want to bring any components around to test in my TZ or check wiring you are welcome.  I am in East Bentleigh.

Thank you for the offer, but I think I'll try and arrange a tech and continue to have a look in the meantime. I'll take you up on the offer if I can't get anyone soon.

Any tech's people can suggest for the West suburbs of Melb?