Well we did the same thing but on a smaller scale as the space was kind of already in place although we had it tanked. We used a non RIBA architect who was recommended by someone who's in the trade, would never do that again and we didn't carry out checks due to recommendation... We've got windows in our basement below street level but I really regret not excavating one of them with garden access. If you don't have windows then I agree with Jonathan plus also think about fire exit. We also had to dig up our patio to get our sofa in so think about the staircase!! Given the size you may also want 2 staircases? Ours is split into a utility room with small store cupboards (room was already there when we moved in), then we have a large room with 3 areas with a pool table, tv and sofa, then a bar with table and seats etc. It works brilliantly as a party space for all ages plus somewhere for my husband to watch sport at weekends and everyone raves about it tbh. We also have an old corridor that we hope to convert if we have the money at some point to a wine cellar (not quite sure how the wine is being funded either!!). We did consider a gym space and decided against it although my husband now wants one a year on! If you have sufficient space upstairs for living and sleeping I agree with Jonathans suggestions which are similar to what we have which I think work brilliantly for a basement. Costs went over budget by at least 25% so blew my contingency! I also made the decision to have radiators run off electricity rather than extend the central heating, not the best decision and in the end not financially either! The work also caused a huge amount of dust/dirt. I think typically you would start a house refurb from the top down (?) but not sure if you'd also do that if you have a basement although it depends if you excavate obviously.

Hi kate2351, We specialize in designing and making bespoke furniture, Please feel free to contact us if you need any help. Kind Regards, A&S Kitchen Wardrobe

Thank you for your comments above. The beauty of being an Interior Designer is the opportunity to cater to different tastes and styles and, ultimately, deliver projects according to clients' wishes. The results may not be to everyone's aesthetic sensibilities and nor should they be, as your home should be subjective and, at times, idiosyncratic, which cannot a bad thing.

You can realistically only use this as a proper room if you have it tanked. I think the advice and quote you have had from the basement specialist is the same advice you will get from any builder looking at it.