Please excuse my ignorance - question about central heating

[FeelingLucky]

Still haven't put central heating on and want to resist for as long as possible by just putting on an extra jumper.

However, during DD's bathtime and naked time, can be rather chilly. Wondered if I would still be saving money if I only put heating on in her room and bathroom and turn off all other radiators in house? Or would it cost the same as having heating on all over house as boiler is on anyway?
We have a combi boiler.

I think that it would save money, as you are then only paying to heat the water needed for the 2 heaters you have on. There will be some loss due to the water in the pipes etc, but will be less than having all the heaters on.

We've got a heated towel rail in the bathroom which really helps to warm up the whole room.