This is a very large segment (in terms of the number of internet suppliers) but a large number of them are highly regionally focused such as WightFibre which supplies FTTP to the Isle Of Wight.
These suppliers are also called AltNets (short for Alternative Networks) and as of August 2022 there are over 70 of them in the UK.
Examples of regional FTTP suppliers include:
KCOM, TOOB, Broadway Broadband, Cambridge Fibre, Zzoomm, Jurassic Fibre, Truespeed, Wessex Internet, etc.
One of the advantages of having a regional ISP as your Internet Service Provider is that they almost all offer FTTP packages (which means very high speeds), competitive costs and generally excellent customer service. A lot of the regionally based internet providers also offer highly competitive packages in terms of monthly cost. Some of the FTTP providers will also offer symmetric connections which means that the download and upload speeds will be the same.