We have a living flame gas fire in our front room. I only ever use it in
desparation and then only on low.

I am about to put a radiator in that room which will complete the central
heating I started nearly 15 years ago! I wonder how much of the heat from
the rad is simply going to dissapear up the chimney, I am guessing it will
be quite a bit.

Anyone any real life experience of this? I have looked at numbers on the net
but these are from people selling solutions.

Ta.