Not true re Openreach monopoly - openreach ftth is approx 51% premises covered, altnets cover 40% of the country (https://labs.thinkbroadband.com/local/uk), so not much in it at the moment.

On top of that, Virgin Media is upgrading their existing 18m home DOCSIS network to FTTH plus their nexfibre build will take them to probably 25m+ homes.

So by the end of the decade the average UK household is going to have access to at least 3 separate FTTH networks.

Only OR FTTH is not symmetrical btw. Everyone else offers symmetrical and YouFibre offers 8/8gig.