Its all about choice. If the good people of Marple decide they would rather buy their goods from a new supermarket then that is their choice. Nobody will make them do it.
Personally, if I want a loaf of bread, I go to a bakers and buy fresh bread. I would not go to a supermarket and buy their mass produced 'plastic' bread.
If I want meat, I go to the vendor of the best quality meat at a reasonable price. I don't go to the cheapest.
But of course if I want commodity items, a bottle of kitchen cleaner, tins of beans, washing powder, I go to wherever it is the cheapest. These are not the things that our local independent shops provide.
But that's the whole point. If Tesco, or any other such concern gets a foot in the door you won't be able to buy your bread and meat in the bakers and the quality butchers for very long.
So you are saying that the people of Marple are sheep who have no ability to think for themselves and make a choice. I disagree. I think there are plenty, like me, who prefer quality to low prices.
Ok, let me explain a few things.
First, Regardless of weither people have minds they will, and this is scientifically proven, shop at the place where the prices are cheaper, which, because tesco/asda/morrisions/lidl/aldi/whatever are huge multinational businesses they can afford to nock that 1p off there prices, and (pardon the phun) "ever little helps!"
Second, people are going to go where there is more choice. thats just the way human nature is.
and third, People are going to go were everything is under one roof, because it saves them time, and it saves them driving around everywhere looking for an item. otherwise why would these stores be in business?