The high street shops rush to close before anyone working a 9-5 schedule can go there and spend money. The stores in retail parks, even the exact same ones whose high-street branches haven't gotten the memo that trading hours were deregulated decades ago, are open several hours later. I don't think I've ever seen a high-street shop in England outside of London that's small enough to have fully deregulated hours on Sunday actually take advantage.

German high-street retail establishments are open a ton more hours every week despite not being allowed to open on most Sundays.