£310 + £150 -= £460 and is still way above cealing price.
Since you already have it, I would do the following:
Re wire
Re plumb if needed
New boiler
See to the roof
Windows ok?
Take down that awful utility room construction
Put in a low to mid budget bathroom in bed 3
Put in a low to mid budget kitchen - establish how sound the bathroom extension is and either knock it down or extend kitchen into some of it and keep some of it as toilet and a small utility
Plaster, paint and floor
New doors, architrave and skirting
TBH given how renovation prices are heading I expect that would take best part of £80-£100
Both #69 and #16 have an extension at the back and sold recently for 372 and 398
Sorry I think you have over paid :-(