BH-03Detect cables and pipes, then isolate if you're unsureSweep the whole fixing area with a cable and pipe detector before drilling — but still treat the ceiling as live, since detectors miss deep cable, cable in conduit, and anything behind metal-backed board. Find your stopcock (usually under the kitchen sink) and check it turns, so you can cut the water fast if you hit a pipe. If you have any doubt at all about what's above the ceiling, switch off the relevant circuit at the consumer unit before you drill.