IP-only != fibre. Try reading my comment above in its entirety. You can also read this for further enlightenment about SOGEA:

https://www.btwholesale.com/products-and-services/data/sogea...

I wish I had a link for the other thing, but it was deep inside some Openreach site that Google don't seem to have access to.

There are multiple options, including internet from mobile phone providers and satellite internet. The affordability and speeds are good enough that it's not a major problem.

That said, there are devices that depend on the old phone network that need to be replaced, such as alarm systems for vulnerable people, but the risk of vulnerable people that can't switch to VoIP services is fairly low, especially as this switchover has been known about for a long time.

Cell phone.