Has anyone had it done? We have had 2 quotes- one from a basement conversion firm (14K) and one from a builder who we know and trust at about 24K. I'm just wondering how the first can be so much cheaper. The only major differences are one is fitting a delta membrane to walls and the other will tank out using Wykamol membrane system. In fact the first includes a hardwood floor, whilst the second is going to put in a 'floating floor' and then we would have to put whatever over the top. It's not cellar, as we live on a hill, and there is a door that opens into the garden, so just the back half is 'underground'. It's accessed through the garden and also steps down from the lounge. It's a hefty space, over 500 square feet or so. I suppose what I'm worried about is that the first lot will cut corners- or maybe it's just the 2nd lot are ridiculously expensive?? I live in the North of Engalnd btw- Any comments appreciated.