Thanks for replying, and you're correct - little knowledge here.
It's a fuse wire box rather than a new switch style one, mid 70's. A new fuse box is on the list to do, perhaps I'd better re-prioritise that.
Turning on a light last night appeared to have \\\"blown a fuse\\\". But having checked the fuses, nothing is broken.
Yet none of the lights work.
When I turned on the light, a green spark came from the switch and a bang noise.
Any ideas? Time to call a sparky?