I think this would be a very good and sensible move. I was in our local M&S Food just before Christmas, doing some of our Christmas food shopping. I would normally go with Mum, but went alone. Although the store itself was relatively quiet (I went at 9pm) there was one family of three shopping and a few more couples. When you have a family of three doing the shop they tend to take up a lot of space along an aisle, and I had to weave in and out. It is much easier to maintain social distancing in a supermarket if everyone is shopping alone.