The more I think about this, the less I know where I stand. As someone who works full time I can't visit shops that open those same hours (well I can as I work in town, but most people can't), therefore not opening on a Sunday vastly reduces the chance I may spend any money there.
On the other side they deserve days off too, and as I said earlier I believe in having common free time. As an example my mum works nights and my step dad days, meaning weekends is their only time together. If more companies worked weekends, more people would find themselves never able to socialise with certain others. That just isn't right in my book, everyone deserves time off with their significant others (whoever they may be).
Perhaps the solution is people like myself should take time off in the week, and make it back up at weekends? After all, it is me that wants to visit the shop. But I wouldn't do that as I like my weekends off (again hypothetical, I work most Saturdays too even if just for a few hours), so I end up buying online instead.
I dunno, someone has to give for our high street to survive but I'm not sure who. I expect nobody to, and we'll lose the lot of them.