This is why local shops have been done so much damage by Tesco Express etc. The problem is that almost every independent local shop is expensive and poorly-stocked. If they weren't, the mini-supermarkets may not have taken off.
To be honest, I don't find the small chain supermarkets much better stocked either so tend to avoid them. I went into one the other day in Leeds and they didn't even have any parmesan cheese ! (Well, only the fresh stuff, and that's no use to me).
A small proper supermarket and an M&S Food are to me absolute minimum requirements for any major city station. It needs both like Piccadilly has.
It is a crying shame that the M&S didn't survive, but hardly surprising if it was constantly pilfered.