The cables you already have for FTTC broadband in your flat are of no use when it comes to FTTP , that copper cable would have been installed from the ground floor to the upper floor at the time of construction , and cannot be used as a draw rope for a new optical cable , it will simply be left in place but redundant, now FTTP is available, even if there were a duct to the ground floor external wall , to get to the first floor requires a cable ran up the exterior wall , and that needs permission from whoever the ground floor wall belongs to ….it says on the survey note for your address that there are potential wayleave issues ( the wayleave is the permission from a third party , in your case the ground floor flat owner ), if they refuse to have the cable that would deliver your service on their wall , there isn’t much that can be done about that .
If FTTP is available, generally if you switch to a new provider they will use the new FTTP network, if you don’t want the upheaval, then you may have to stay with your current provider
