I feed a family of 8, so am always really keen to find the bargains without losing quality.
For lots of things, I shop at Costco. I like it because everything is good quality but a great prices. I go roughly every 6 weeks and spend about £350 a trip - it's the same regardless of how much meat, wine and other expensive items that I buy.
I use Sainsbury's for everything else, and spend less than £100 a week, unless I'm entertaining.
I find it really hard to make lists for Sainsbury's as they have so many deals once you get there. It would be mad for me to plan out a meal in advance, only to have to pay the full price for the main ingredient, when they have BOGOF on something else. I do stock up on the BOGOFs, though. The deals don't seem to make it to their website, so it makes their online shopping less attractive.
I've tried Tesco and Asda, but they just aren't worth the extra journey for me. I do pop into M&S and Waitrose when I'm in town though, but just for that night's meal. I don't "get" the quality that other people see in Aldi and Lidl. I go there very occasionally if I see something in their weekly offers that I'd like (non-food), and will, of course, fill my trolley - but am invariably disappointed. There is no way that I'd buy their nappies or toiletries.
We have a market twice a week, so I will often go there for fruit & veg - getting buggy-tipping quantities for about £8.
I spend about £40 a week on wine - a great opportunity for cutting back on the budget.