I'm just trying to get a rough idea and I thought it would be useful to ask any mnetters who've had this work done.
We've got a knackered, leaky conservatory. Boiling hot in summer even with the windows and doors open and freeezing in winter even with the radiator on.
I'd love to be able to have it knocked down and replaced with a bricks and mortar extension of a similar size (about 15ft by 12ft.)