As a non-christian the idea of having Sunday as a day when everything shuts down seems fairly arbitrary. Although having said that we are technically a Christian nation, so I suppose that has to count for something.
Also, as I've seen stated in several places it would be ashame to see any loss of smaller shops as a result of deregulation, but if these places are relying on Sunday trading to keep themselves afloat then surely something is wrong here anyway and they despirately need to address ways of increasing business. Whatever happens the supermarkets aren't going to go away and they are finding ways around the Sunday trading limits anyway.
As such I'm failing to see the benefit of these restrictions are. Yes, people need at least 1 day of rest a week, but if you don't follow the Christian religion, why does this have to be Sunday. There are many supermarket workers who would much prefer to have a day off during the week and get the extra pay for Sunday work.
I don't personally see any difference between a Sunday and a Saturday, so cannot see why the rules for the 2 days should be any different.
Anyway, here's a pole on the subject:
Should Sunday Trading Be Deregulated?