It doesn't matter whether you yourself would feed in a shop or not, the point is that should you choose to (or should your baby decide its hungry) you have the legal right to feed your baby there without being turfed out into the rain.
Our nearest Sports Direct is on a retail park with no outside benches and no nearby cafes. If I was in there shopping and DS2 needed feeding, I'd feed him and tough shit if anyone has a problem with it.
When DD was a baby she was FF, we took DS1 to Sports Direct for some cheap trainers for our holiday. She needed feeding so while we were sitting in the bench waiting for them to bring DS his trainers I picked her up and fed her a bottle. There was no issue. Why should breastfeeding be any different?
I'm sorely tempted to take a trip there and exercise my legal right to BF in public.