I'm always after markdowns, so it's mostly late(ish) evening shopping at Morrisons, Co-op and Tesco for us. I also shop the markdowns at our corner shop and the fruit and veg markdowns at the market here. Sainsbury's is ok on their markdowns, but they don't mark things down until way too late for me to go since it's a mile and a half away and I'd have to walk it. Aldi and Morrisons are the only places I'll pay full price for something. The customer service is fairly good at all of our local stores.
The only quibbles I have against Aldi are that they never mark down fruits or vegetables, and they never have anything in stock on Saturdays, just rows of empty bins!
I cook and freeze a lot of things, plus do preserving and canning, thus why I'm always after the mark downs. I also have time to make rounds of certain stores on certain days, which I know some people don't have the luxury of doing.