I would say way more than £100k.
We are in €, but started renovating around 5 years ago, so spread out. It’s had a fair bit done, but still hve loads of old windows to replace, insulation hasn’t been done yet, cellar needs damp proof work and lots of other bits ie most bathrooms haven’t been touched.
We are on around €150k, but probably need another €50k. And the main demo work and structural fixes were done 2018-20 ie before materials increased a lot.
Roughly:
€65k - fixed east side of house which was an extension about 40 years ago. Upstairs x2 bedrooms and bathroom were gutted, new floor beams, new walls, new staircase up, bathroom, all new electrics that side and plumbing. One old patio door blocked up, new window. old shower room demo to become new hall and landing.
€20k - new 5m sliding doors and 3m front doors glass either side.
€17k - new communal heating system. Old oil demo etc. that’s new boiler and water tank and piping.
€20k - new kitchen ( plus all new plumbing, plastering and appliances) its a small kitchen, mid range
€15k - the rest of the house all rewired, replastered and painted
€5k oak flooring - fitted ourselves and sourced reduced ( was going to be triple otherwise)
Then there’s been other smaller projects and fixes over the last few years and still stuff to do. We couldn’t afford to do it all in one go. There’s been no extension in that either. It’s approximately 200m2