Water is dripping from the ceiling when the central heating is on. If the heating remains on the drip becomes a gush (the ceiling has fallen in under the weight of water). When the bathroom floorboards above have been taken up all water plumbing was dry even when the heating was turned on again. Floorboards in adjacent room was also taken up - all pipework was dry. Can't turn on central heating (combi boiler) as water continues to leak into the kitchen ceiling. Anyone experienced this and found the cause?
You have a leak, obviously. Water will travel along pipes, wires, framing, etc so it doesn't mecessarily have to be leaking right above where you see the water. It could be a hole in a pipe, bad fitting, etc.
You're going to need to rip up your ceilings (usually easier than floor since it's just drywall versus a flooring material) to find out where it's coming from.
Letting it get to the point where the ceiling collapsed wasn't a good idea. Wet material grows mold. After you fix the leak there is a good chance you are going to have to replace a lot of other rotted or moldy material.