Not quite the same situation as yours, but a few months ago when I was tracking down how far FTTP had spread through the town where I live, I came across this pair of semi-detached houses where the house on the left can get FTTP but the one on the right can only have FTTC.
They are both fed via overhead drop-wires from separate poles which are connected to different cabinets.
That must be frustrating! That postcode is served by 3 cabinets - 2 of which are FTTP. If you live in that postcode, you have a 60% of being able to only get FTTC.
It's interesting looking at BT's data for my area (Cabinet P44 in Milton Keynes), there should be 100% FTTP availability. But it looks like less than 40% based on the searches I have done so far. BTO need to clarify what the issue is for our/other areas in MK.
As Gareth has already pointed out in the BDUK data shows Willen as designation grey. In theory, everyone should have access to superfast broadband but they don't. There are also anomalies like my street being designated white despite already having FTTP.