Savings like this are only possible if you carefully monitor which rooms you need to use, keeping those at a suitable temperature. Keep the thermostats on "frost free" or just above for other rooms. Night storage heaters are very wasteful when a very warm day follows as you've already heated the heater and that heat is wasted.
Bathrooms are different to all other applications. You must not have electrical sockets in a bathroom, the heaters to use in a bathroom are sealed panel heaters or oil filled splashproof radiators. I also use instant water heaters so water is only heated as you want it.