After some tinkering yesterday, I think I determined that the lack of brake light, indicator and intercom I was experiencing was down to a bad connection (intercom is powered from switched live to brake light) . It would appear that a previous owner felt the need to cut the wire feeding the aforementioned items from the fuse box, and put badly fitted crimps in the circuit.
After some investigation, and re-terminating both the light feed and the feed to the intercom (which was just a stripped wire pushed into one half of the rear brake switch connector, and held in place by the other half!), it would appear that all is well again.
Next job: clutch fluid level check, and top up.