During 2021, our local Waitrose (in Dorset) was given a major refurbishment which, amongst other things (extension of the café, new freezer cabinets, installation of self-checkouts, so on) included the creation of a separate exit from the store. So they can now implement a proper one way system if they need to, but I assume the separate entrance / exit idea was part of the original "plan" anyway, not necessarily with Covid in mind. Checkout screens have never been removed since their original fitting, but there is now a return of part-time security, albeit just the one guy smiling serenely at you as you leave the store. There's no attempt to limit numbers in store. The 4 new self-service checkouts are individually screened.
The only supermarket with a traffic light that I visit is Aldi, and I've never seen it on anything other than green.
One smaller supermarket cum Post Office (OneStop) is prominently indicating masks are compulsory; that may have something to do with the main Post Office organisation who locally have had a draconian approach to lockdown throughout. Mask-wearing generally in local supermarkets is now pretty much back to 100%, a distinct change from a visit I made to a local Asda in November when, as far as I could tell, I was the only punter wearing one!