I don't remember the 50's. Apparently it was a grim time; ration books, smog, no proper heating, pubs shut more than they were open, drab clothes, damp houses with musty wallpaper, capital punishment, outside toilets, Winston Churchill long past his best and rubbish music. A time when you considered yourself fortunate to even have a dad as there was a good chance that he'd been killed in the war. Shop-keepers on every corner charging high prices and opening and closing when they wanted to. That was a major reason for the advent of the supermarket, poor levels of local service in the 50's and 60's.
I don't know what Henrietta is buying from the co-op to see her bill go down. Every time I go in it which is not often, I'm actually shocked at the sky -high prices. I vow not to go again but of course I always do.
If local businesses (which I try to use ) can't cater for local customers then local customers will go elsewhere. It doesn't matter what the shop-keepers are doing on Wednesday afternoon, that's none of my business. if they want to watch Jeremy Kyle or play with their kids, then that's entirely up to them. What is my business is that they're not open when I want to buy something that they sell - so I'll get it somewhere else.
A supermarket, the right one in the right location, not a great big, clinking, clanking Asda on Hibbert Lane would bring competition for the co-op and the local buys and there is no doubt whatsoever that one will be coming to Marple in the near future. So just accept it.
In my view this will not be the death knell for local businesses in fact it could even bring additional foot-fall into the town and extra revenues for local business...but if you close on a Wednesday afternoon.... then perhaps you should relocate... back to the 50's.