Hi @getitdonet
I’m in Surrey. My doors are from www.origin-global.com. As my works were knocking three rooms into one, moving water, gas, drainage, boiler (and new boiler), underfloor heating, new appliances (retained my American fridge freezer), new door into the room, 4 RSJ, large amount of tiling and new kitchen plus bifolds etc, it worked out to 100k and took three months (although we are STILL waiting for small things to be done such as more tiling either side of overmantle, lighting etc) BUT we know we have dramatically increased the value and saleability of our house. We had a number of estate agents in prior to doing the work, discussing if we do this or that or nothing, what would be the value. We also had architect fees, surveyor, structural engineer fees as well as some to council for various certificates. (No planning was needed though)
If you need to move gas etc and have more RSJ other than the bifolds, the cost increases dramatically. Also, smaller bifolds may not need RSJ. We have 9 Metres of bifolds so needed massive RSJ
The kitchen units themselves were 11k and come unpainted. I painted them myself which saved a few grand. You can save loads that way and the quality is amazing. Hand made kitchens of Christchurch is where my kitchen comes from.
I would suggest getting in some builders and they can give you rough estimates. Don’t use cowboys if you’re knocking down walls and be sure to get the builders by word of mouth from people who have actually used them.