I believe the current version of the Ofcom Access Network Frequency Plan (ANFP) prevents the full frequency range of VDSL2 profiles 8c (legacy) and 17a (current) to be used within exchanges.
The goal of the ANFP is to minimize interference between the various transmission systems. I understand from reading other posts on this forum that the restrictions on VDSL2 are there to prevent interference ADSL2+ services served from the same exchange.
I also read about some practical issues. If the line is too long there will be no throughput benefit over ADSL2+ (VDSL2 effectively falls-back to ADSL2+ on long runs), and the line length from the VDSL2 DSLAM to the edge of the exchange can easily be 200m.