I think you need to distinguish between "Can you buy BP in ..." and "Is BP seen as a part of local cuisine in ..."

While you can get it almost anywhere in the UK (and many other pig-keeping countries will have their own versions) I think it would be fair to say that the north, and especially the northwest, would be the area which would regard it as a regional speciality.

Your true question seems to be are you in the North, now that you are in Derbyshire. To those south of the Wash, you may seem to be so, but what would they know? Tell yourself you are doing missionary work in the badlands of the Midlands border.

I'll get my (borrowed) northern coat, it's hellish foggy on the N.Yorks coast today, and cold for a midlander by birth.