More leased lines decreases changes of VDSL2, i.e. those with need of leased line quality guarantees would not get those from a VDSL2 service generally.
5 Mbps sounds as if something is wrong if on cab 24 as its very close to the exchange and 10 to 19 Mbps is more what you should expect, so time to dig out the ADSL/ADSL2+ stats.
Nine other cabinets were done via the CDS project, but phase I is coming to an end, and BT does not have a phase II contract, so over to the council to explain what the options will be.
If you want Openreach, and not Virgin Media or someone else then there is the community funding route if you can get enough local interest.