(** Pedant's corner: It's not actually a VPN, there's no encryption and it's using standards that are moderately common amongst telcos but anyone else would consider wierd. But you get the idea).
It's only weird if you swim at Layer 3. If you dive into Layer-2 with me, then it's all pretty standard. Which it sort of has to be given Openreach's structural seperation from the BT Mothership. So my point was because BT has SMP (Significant Market Power) wrt access products, I could buy services from Openreach. So for Radford, a little something from Openreach's 'Superfast' or 'Ultrafast' line. You can register to get the gory details and pricing.
The other bits of BT (Business, Retail and Wholesale) buy the same products from Openreach on the same terms as it offers to competitors like Talk Talk etc who create their services using a mix of their own infrastructure, and services from Openreach or Wholesale. So like I said, to get access to those new Coventry FTTP builds, you'd have to deal with Openreach and build your own infrastructure, or deal via Wholesale or a competitor who's taken Openreach up on something like their bulk fibre offer.
But such are the joys of a regulated environment. Like BT's death-like grip on their infrastructure so it gets to keep dark fibre options away from competitors.. Industry is slowly chipping away at that one though.