For Brits of Polish origin or native Poles
For anybody probably. Most larger food shops and some smaller ones in my home town stocked Polish products, sauerkraut, gherkins, jam, tinned meat.
Plenty of Poles and Ukrainians there (who came after the war) however as I remember there were some many things from Poland that others must have bought them too. We always had Polish products at home, especially gherkins and jam but also sauerkraut sometimes. They started to disappear from the shops after Chernobyl due to consumer reluctance and when the UK joined the single market in 1990 pretty well vanished completely.