Ford Mondeo electrics went funny, couldn't start

Doors unlocked normally. Tried to start and nothing happened. Some of the warning lamps were on, but not the no-charge lamp. (I can't remember whether they were on before I put the key in, but think not). Warning lamps stayed on with key out, or in in any position. With key in or out, various things that should not have worked did e.g. wipers, windows, headlamps.
Battery could getting old, so thought it might be low and tried to jump-start. No difference. Had the idea of disconnecting and reconnecting the battery. There was a click on reconnecting and everything was back to normal. That was 24 hours and several trips ago.
Anybody had anything similar happen?
No doubt there's a good chance it will happen again sometime and might not be fixed as easily.
I'm reluctant to take it to Ford as they might say they know what to do and change one of the electronic modules for plenty of £££. But as the fault is intermittent I won't be at all sure they fixed it, unless it happens again when I'd know they hadn't!

Grateful for any suggestions.

Roger