It's all down to demographics. Please see article here:-
http://www.guardian.co.uk/lifeandstyle/2004/mar/12/foodanddrink.shopping
To quote from the M&S section:-
'Rupert and Felicity, again, are most likely to patronise Marks & Spencer, lured there no doubt by the dearth of piped music, a soothing green and silver livery and a snooty aura. "Interestingly," says Gladding, "Marks' food shoppers are more upmarket than the clothes shoppers." Least likely to visit M&S are Wayne and Leanne (the "municipal dependency" archetypes), who live on large, low-rise estates far from the centre of the city, and represent 6.7% of UK households. The second most likely group to shop at M&S are Darren and Joanne, the happy family.
At the food branch in Golders Green, the customary range of frighteningly unhealthy desserts and unsatisfyingly crunchy ready-made pizzas are being snapped up by a well-groomed bunch. An orchid-buying and very pregnant book editor, on maternity leave from her £35,000 job and whose husband works in the City "and earns more than double what I do", says: "I know it's a cliche but my mother shopped here and so do I. It feels traditional and right. I don't get all the weekly shop from here, but I like to buy a few things. Treats mostly. I like the staff and, without wanting to sound snobby, the other shoppers are well dressed. There aren't a lot of people here who are ... " Common? "You said it. I couldn't possibly comment."
Another woman, loading shopping into her H-reg VW Golf, adds: "This is a place for luxuries, not the staples. But it makes you feel good to shop here. You feel richer than you probably are." She declines to tell me her job or salary.'
Doesn't sound very 'Dover' to me?
(But then again what the Hell is a branch of Waitrose doing in Ramsgate!!!!!
