Problems with lights: We once came back from holiday; the weather was cold, and I'd had the bright idea to save fuel (and reduce fire risks) by turning the heating off. When we got back, three of the ceiling lights, erm, wouldn't, so I worked out which circuit breaker to turn off to isolate them, and we called the electrician. When he came, much to my surprise, all the failed lights worked.

When the electrician stopped laughing, he explained that LED lights, and some compact flourescents, don't work properly when they're cold (by then, the house had warmed up). He wouldn't take monies for the visit, but we funded his next pint for the call-out.