All such Tesco mini-markets are very conveniently located and you can always find what you need in them. And if something is missing, there may be a Sainsbury's store nearby.
I always preferred Tesco because of its proximity to the hotel, or it was almost always on the way to the hotel.
We bought ready-made salads and juice for dinner. Surprisingly, in this network, only beer and wine of 5-6 varieties are made from alcohol. We couldn't buy gin in central London for a week. Miracles!