Until now the public have not really taken to wearing masks in shops. There have been a few but their numbers have dwindled over time and they are very much the exception. This is purely anecdotal evidence based on my shopping trips, but seems to chime with other posters' experience.
I had to go out for work this morning (for the first time since March, but don't get too excited as I was just collecting a replacement piece of equipment!). While I was out I popped into Morrisons and was surprised to see that more people than usual were wearing masks. Could just be a coincidence or could be linked to the government announcement.
Personally, I would prefer not to wear a mask while shopping. However, the scientific viewpoint does seem to be changing as we learn more about how Covid-19 is transmitted. I will happily wear a mask if it means we can stick with the 1m distancing rather than 2m, continue with the shorter queues (or no queues) outside shops, and avoid potential local lockdowns. I think some of the issue (maybe this is a male thing) is people don't want to look like the odd one out. Back in February when I saw someone wearing a mask, my head turned. So as it becomes normal I think people will become more relaxed about it.
I do sympathise with those who have medical conditions which prevent wearing a mask, as they will be the 'odd ones out' now and the people who cause heads to turn, even if not in a nasty way.