If your individual flat/apartment has FTTP availability what does the survey note show on the wholesale checker , use the address option and post the results.
https://www.broadbandchecker.btwholesale.com/#/ADSL
A typical entry for a new build house ( fully ducted ) shows
Our records show the following FTTP network service information for these premises:-Single Dwelling Unit Residential UG Feed with no anticipated issues.
Your address will differ , but providing this information will be illustrative.
There will be a huge variety of possibilities with flats/apartment complexes, depending on the number of dwellings contained within the MDU ( multiple dwelling unit ) ranging from a couple of flats , to a high rise containing scores of units, FTTP service normally mirrors the existing copper network, but not always.
Larger MDU’s , ones that tend to have a single point of entry to a foyer, with lifts and or stairwells to higher floors and the individual units front doors , the existing copper network will have been provided when the building was constructed, so retro fitting FTTP will be very difficult, and tend to be excluded from the normal FTTP build , and dealt with separately .
In these cases all stakeholders ( leaseholders , landlords , building management etc ) are consulted before work is planned , and obviously if any party refuse or ask for payments , then the building is simply left out of any scheme.
If there is a neighbouring flat that already has a CSP fitted on an external wall , I would suggest they never contacted the building management, as you have done , but simply ordered service, the ISP and Openreach would proceed on the basis that the person ordering services has the necessary permission, obviously that CSP could have been provided on behalf of any of the ISPs that uses Openreach, not necessarily BT.
I suspect this neighbour ( and presumably yourself) are part of a smaller type MDU , so potentially, especially the ground floor units , could have individual ducted feeds , and those units on higher floors could be served differently, potentially the higher floors ( especially if the MDU isn’t particularly high rise , ) could need permission from the ground floor units to run a cable over their property to reach the higher units.
Is the building only ground floor and first floor flats ( for example ) perhaps you can describe the type of building in these terms , and if any visible existing copper network exists , like blocks on walls with copper cables to individual units ( external DP’s )
