Our conservatory is fully glass with the sloping glass/guttering effect where you can hear the rain loud and proud. It is the length of our full back of house (quite big).
We were quoted £20,000 for a new pitched roof, quad bi-fold doors, new half bricked up all the way round, and take down of complete external back wall to make one big open kitchen. Essentially turning it into one big fancy useable space. No wiring or plastering included in this price (just the bare bones/foundation/roof and brickwork) as my husband would do the rest. Other quotes were about £25,000, £30,000. Our neighbours had theirs done for £32,000 and theirs look stunning.
For us, we decided as we had only been in the house a year (now two) we would not go ahead; we had other things we would much rather spend our money on.
HOWEVER due to having teenagers and needing a workable space for them, we framed up, insulated the ceiling & then my husband put the polycarbonate sheets up, then did the electrical work for lighting. We had a radiator added, track & thermal curtains added, and then had a dehumidifier popped in the room (takes the damp edge off/gets rid of condensation wonderfully).
It has proven to be a very workable space. Looks/feels really warm and cosy, surprised me really. Didn't think it would work this well. Another plus, our clothes dry quick in here too. We'll save up for the big job if we still want it in the future, but our set up works for us all.