Local convenience stores are indeed usually more expensive than their large equivalents. I'd be pleasantly surprised to find that the Sainsburys in Forest Hill has the same prices as the huge one at Bell Green - I don't know.

But if Morrisons open a few doors down from the existing Forest Hill Sainsburys and are not competing on price, they're idiots and deserve to fail. They're not going to get by just on being marginally closer to the station.