Hi Heather! At Urbanist Architecture we love helping our clients get planning permission and turn their dreams into reality! We are a team of planners, architects and engineers and we had the chance to work on over 500 projects in London that are similar to yours! We would love to help you progress from a ‘’pipe dream’’ phase into something real and amazing. Just to give you an idea of what we do, please visit our website: https://urbanistarchitecture.co.uk/ After getting in touch with us, we will carry out a free initial feasibility report and will send you a quote. We will help you formulate a brief, prepare design options and submit your planning application. We are experts in our field so we will be advising you along the way in order to deliver your dream project stress-free. Don’t hesitate to contact us!

Like Jonathan already stated, this isn't going to be the spacious luxurious master suite you have in mind. If the majority of the stairs is on the floor below, you could have this layout, for example. The pale grey is the area where you can't stand up straight. Again, really really make sure the joistst can handle all this weight! Otherwise just turn this into a kid's loft and make a nice spacious family bath on the bedroom floor. With a separate toilet of course. ;)

Hi @Emma CW If it's any use as a very rough comparison, you can see our project here: https://www.houzz.co.uk/discussions/5865541/utility-kitchen-design-feedback As we've come closer to obtaining quotes (planning with our council took 6 months due to Covid delays), it seems we're likely to be looking at £125k (or about £2500 per square metre), excluding kitchen. Our U-shaped kitchen, which fills a space roughly 4.5 X 3.5m is looking like an additional £20-35k fitted (range based on direct-from-manufacture web retailer, to bespoke local supplier), with mid-spec appliances and sourcing our own quartz worktops. No idea how one might get a high spec kitchen for £5k as suggested by Base 2 (- appliances alone could easily cost this). Do note that we require demolition of two existing structures and we have limited side access to our property (i.e. little room for machinery to excavate foundations). Of course, interior furnishings, landscaping and contingency costs will all be in addition to the above estimate. When we went into this project, after reading years worth of home building/renovation magazines, we thought we'd be able to realise our plans for under £100k. Unless we were going to actually do the work ourselves, it quickly became apparent this wasn't realistic when ringing around for quotes on some of the big ticket items (e.g. glazing, kitchen, groundworks), so my main advice would be to speak to your architect/designer about probable costs based on comparable projects they've worked and ask a couple of local builders to give you a rough guide from your plans.

I was one of the original poster. Eventually in our case, building control wouldn't allow this - they originally OKd the plans, but then wouldn't allow the removal of the ceiling from the box room. There was a "galleries" approval that we explored but they weren't having that either.