Column radiators cost to heat house

[Brownebear]

We have recently installed column radiators (stelrad regal) pretty much throughout our house during renovation/extension work. We choose steel radiators for the classic design. I knew they would contain more water than traditional radiators but that information isn’t really advertised and I just focussed on btu’s and made sure I oversized them. Now we are still without flooring downstairs, so heat loss will improve once complete.
My concern is the cost of running the system with the upcoming price rises.
My boiler is a worcester green star 24ri with an unvented cylinder. House is now a large 4 bedroom house and on checking meter reading we appear to be using 4 cubic feet per day during January.
Due to amount of water in the system it now takes longer to heat the house and therefore costs more. Any advice on heating the house as efficiently as possible? Or am I screwed?

 

[ShaunCorbs]

More insulation and better windows

Only way to change your heat loss eg use less gas to heat your home

Your boiler will still only use 24kw so changing from normal to column rads won’t add too much cost on start up but they will hold there heat longer so plus and a minus so even themselves out

 

[Brownebear]

In the process of new double glazing to front, bare floorboards downstairs at Min on a suspended timber floor. Will be overboarded and then lvt. If I'm going to make any changes, would probably be best to do so now.
My concern is Surely with the water volume being a lot greater it will cost me more to heat said water up and to also keep the water at temperature. Or am I wrong?
Once all building work is complete, would I be better having heating on for only when in and having to heat all the water up for desired result.Or leave it set lower and running more frequently so water doesn't completely cool down?

 

[ShaunCorbs]

Tripple glazing shop around for high u valves

Insulation under the floor boards eg rockwool they have a good guide how to do it etc

As for water heat up times you won’t be able to tell might take 5 mins extra to heat up but will stay warm for 5 mins more after as an example