When I lived in Sheffield, P... shop was used simply as a synonym for 'corner shop' or 'convenience store'. Even if the owners of such a shop, and all its staff, were white, people would still say that they were going to to the local P... shop.
I even heard the young daughter of the (Indian) owner of such a store, when answering an enquiry from another girl about what her parents did for a living, happily reply with "Oh, didn't you know? Our family run the P... shop up the road".