Whilst our boiler has been inoperative, we have had to make do with
just the living room radiant gas fire. With door closed, it is more
than warm enough on 1/3 of its 3 bars lit, but the rest of the house is
cold. Aside from the heating, the gas boiler provided for all our main
hot water needs too, washing up, cleaning and baths. With an electric
shower. The gas heater has been lit roughly for the same amount of time
as the boiler would be providing heating in the place.

Cooking is via gas, so unaltered.

I log gas, electric and water consumption every week, on a Sunday. The
boiler failed mid- week, so this is the first full week with no boiler.
In the previous two full weeks with boiler in operation, total gas
consumption was £14 per week. In the this full week of no boiler use
consumption was £7 - so about half the cost if we put up with one room
heated, versus the whole house being comfortably warm.