Ours is 5m x 3.6m. We dug the footings and concreted them, laid the stone, acquired the polystyrene sheet insulation and DPM (the estate we live on was still being built, so only cost us a drink!), laid the floor slab ourselves, got a couple of brickies on site to do the dwarf wall (though we had to buy the bricks and premix mortar). A friend of a friend works for a firm that makes the consevatories, so we got that at cost price (including a new pair of uPVC doors to replace the existing patio door) and their price included tiling the floor (we bought the tiles). We have left the brickwork natural (so no plastering). A mate put in the electrics. Including cane furniture, lights etc we spent about �8,500. So I would say, unless you are willing to do a lot of it yourself, your quote isn't a bad price as it saves you the hassle of finding the time to do it yourself.