We start ours in 2 weeks. Live in a similar sounding house, 2 bed victorian mid terrace.
After a couple of quotes ranging from 20-23K we have settled on a builder doing all the structural work, two floor beams, ridge beam, floor, rafters, stud walls, stairs etc. and I’m going to finish off doing insulation, plasterboarding, electrics, plumbing, etc. Works out a fair bit cheaper (on paper), might be worth an option if your are confident diy.
we have had plans done by architect (including ground floor extension) and structural engineer calcs, all signed off by building control.
If it all goes horribly wrong expect to see my posts on here whinging about it!