FTTP on Demand
is, in principle, available to order anywhere that has FTTC, as long as it's not a multiple dwelling unit (e.g. flats).
It means paying Openreach to install a custom build-out of their FTTP network to your location. The cost depends on the distance and complexity of the installation, but the minimum quoted these days for a simple install is about £8K+VAT, and it can be much higher
You pay up-front, and there's no guaranteed installation time: typically it takes 6 to 18 months to complete.
There are a handful
of ISPs who will sell you FTTPoD, such as Cerberus
You will have typically a 12-month contract with your initial provider, after which you can switch to a native FTTP service from any ISP that sells services over the Openreach FTTP network.
The piece of FTTP network that you paid to build will normally also make service available to a few neighbours - those who are served by the same pole or footway box - and they'll be able to order native FTTP from day one. It's possible to link multiple FTTPoD orders to build to a larger area, but above 2 or 3 you're likely to be better off going with a Community Fibre Partnership (CFP).