I just checked, and found that I'm now enabled for FTTPoD too. That's Harrogate, North Yorkshire, and meets all 3 of your criteria.
I'll take a pass, for now, though.
Following your theory, I quickly checked on the other two exchanges in the town - both of which (presumably) treat the main Harrogate exchange as their parent...
- Starbeck exchange, which has no FTTP areas, seems not to have FTTPoD as an option
- Oatlands Mount exchange, which does have some limited FTTP availability, does have FTTPoD as an option.
Limited sampling, though.
In the original rollout, Harrogate came first. Starbeck was added a couple of years later. Oatlands came later, and only as part of BDUK.