I always wondered if that was possible, with the PPPoE (or oA) connections from the home terminating at some ISP hosted equipment in a handover exchange. I assumed there would be thousands of connections from all over a large region of the UK, coming together.
Large ISPs have POPs all over the country, with separate IP pools, so can geolocate to that level. However a small ISP may only have a single POP, with PPPoE/PPPoA sessions backhauled as L2TP over BTW's network.
I find it amusing when I am shown clickbait adverts like "Pensioners in Pinner are snapping up brilliant new hearing aid". I'm nowhere near Pinner - but that's roughly where my ISP (Cerberus) are based.