If water’s coming through your ceiling right now, deal with that first. Put a bucket under the drip and towels along the skirting, and if it’s anywhere near a light fitting, switch the electrics off at the fuse box before you do anything else. Once that’s sorted, the checks below will help you figure out where the water’s actually getting in, what’s likely caused it, and whether it’s something that can wait or needs a roofer out today.