we got a loft extension in 2022 and paid a similar amount. We went with a company who specialises in loft extensions so they kind of build them to their spec, but it was a one off fee, so we don’t get any extra surprises an they project managed the whole build. we could have got it cheaper, but we would have been responsible for finding some of our own trades folk for some jobs plus getting the Building control sign off and i didn’t want to do that.
a few tips from me:
we needed replacement fire doors throughout the rest of the house, which was included in the price. Bathrooms aren’t covered, so we ended up having to pay them extra to replace the bathroom door so it matched the rest of the house.
5 plug sockets don’t seem enough. our company fitted 10, which included a shaver socket in the bathroom. We upgraded to usb ones so paid the difference.
they fitted us 3 large velux windows. Many loft extensions i’ve seen fit 2 slightly smaller ones, but i love having 3 as it means the sloping wall lets loads of light in.
for our eves storage, they put in two doors at opposite sides. would recommend this as it’s much easier to get to things stored in there.
the trades folk were contractors and they told me they get paid a day rate, by the lift company so it didn’t matter to them how many plug sockets they fitted, which is why you may be able to haggle on some of the extras.
the only tricky thing was the bathroom as whilst they would install it, they wouldn’t tile the shower. their recommended tiler let us down, we we had a few months or not being able to use the shower.
we decorated ourselves as OH is a competent decorator. We also had to pay for flooring plus the bathroom suite.
the final thing is to make sure you get your party wall agreement in place if you need one. our company had a last minute slot as a scheduled build was delayed due to party wall issues and they offered ut to us, which meant they got started right away.