Before we talk about what to do in a freeze-up, it’s worth considering what you can do now to insure against ever having one.
The elementary precaution is to lag all pipes that are in a risky position – those in the loft, and those fixed to outside walls in unheated rooms, such as outhouses or an outside WC.
There are several kinds of pipe-lagging on the market that you can get from hardware stores and builders merchants. If the pipes are accessible all round, you can wrap them with an insulation bandage, which should be further protected with a waterproof covering in damp situations.
This won’t be easy where the pipes are fixed close to a wall, but you can buy foam-plastic material formed into a tube. When slit down the side, it can be slipped over the pipe. Alternatively, you can box the pipes in neatly with hardboard and timber framing after insulation has been applied.
If you do it this way, you can ease a strip of glass fibre insulation bandage between the pipe and the wall and tuck another strip around the front, which will be held in position by the hardboard cover.
For protecting the cold water cistern in the loft, there are special lagging kits made in many standard sizes. If you are insulating the roof space (and you should), you could bring the insulation material up around the cistern.