Korona

This is a great shop. They've got a huge selection of food & drink and the staff are great at explaining anything about their Polish brands that's unfamiliar to us Brits.
If you're used to Brit grub - fish & chips or whatever - you'll like their stuff. A lot of it is simlar to what we're used to but slightly different, so a nice variation on Brit food.
Their prices are good, too. I've started buying some of their fresh meat & veg combinations and they do generous helpings at prices that match or beat anything you'll find in the supermarkets.
Good food, fair prices, nice people.