One of the biggest problems with the UK, is how we bog ourselves down with horrendous levels of bureaucracy and associated costs, which end up making large scale projects cost prohibitive, for the most part. Mostly down to archaic planning rules, and the insanely wasteful and overly expensive contractors who'd be required to deliver it.
Essentially, if the UK decided to roll out FTTP everywhere - it would just be a great big rip off, the cost would be incredible, because the UK simply can't deliver large scale projects, without making a total embarrassing mess. (HS2, Brexit contracts, test and trace, channel tunnel, etc etc)
I've done work for most of the UK based ISPs, (core networks, broadband, edge and mobile) <I used to be a consulting engineer for Juniper> and I did do a job for one of the most popular rural broadband providers once. Essentially - the cost of digging fibre consumed all of the government funding and their own money, to the point where they almost went under and could barely even afford to buy routers. Laying fibre was simply so expensive, to me it seemed silly, and I could never understand why it couldn't be made cheaper.