The Natural Philosopher coughed up some electrons that declared:

I have a roomstat set to 18C and SWMBO says its 'fine with a jumper on'

By running 24x7, that 18C is utterly even: with timing, I used to feel
cold until the stat showed 19-20C.

That's interesting. Do you have a feel for whether it was much more
expensive to run at 18C all the time.

BTW - found an approximation formula for U-values of uninsulated floors:

http://www.warmafloor.co.uk/knowledg...insulation.asp

(some good reading material there)

U = 0.05 + 1.65(P/A) - 0.6(P/A)^2

where P=length of exposed perimeter wall, A=floor area.

I've got IIRC a P/A of 0.5, so base U-value of 0.73.

I'll try some numbers with that after I call the gas/leccy boards...

Cheers

Tim