It depends on what I want. I get a fair amount at lidls/Aldi. They both do nice chocolate, excellent non bio laundry liquid, continental meat and cheeses, good value fish.
I then go to both Sainsbury's (never any issues with them) and M and S...I like their 3 for 7 deli items, cheeses and veg that I might not find elsewhere.
I only have access to a Tesco metro...they are my last choice, and rarely have anything I want or need.