Yeah, I have a weekly shop with Ocado. It builds it for me, as discussed upthread, so I don't forget anything, and I edit it. Spend £50 a week and eat very well for two adults (both at home 24/7) plus waifs and strays. I meal plan but not rigidly. I tend to buy a pie, a piece of fish, some nice sausages, a posh ready meal, something on offer, etc, six or seven things with something for the freezer, and then eat them in best-before order.
If you're a bit mad (I accept I am), you might look at what stuff you get tricked by and shop differently to avoid it. You don't get much tempted by bulking offers on fresh food because they just don't, you know, do them for those things very much and when they do it's not very alluring. I mean. If you buy a pie, you might want two pies, right, but you don't want four. Who wants four pies? A wall of pastry! They'd just go off. You'd just end up throwing it away. Same with potatoes. You might want a 12kg bag, but you don't want two. So they seem to reduce the prices on those things rather than bulk offer them massively.
I guess that's why they stick them on crisps and drinks and fruit. You don't think of them in terms of meals, so you have no upper limit in your head.
Milk keeps for a week actually, unopened. It's fine. I buy 10l once a week. Don't really eat bread or snacks. Keep spuds in a root store. Etc. I have no need to shop more frequently and we rarely if ever throw food away.
But I don't have a car so if I do go to the supermarket, what I can spend is limited by the size of my bike basket. Handy!
Waitrose is sometimes cheaper than Ocado when they do crazy offers on their ready mades, but the problem is (with my store) that they substitute massively. I've had Waitrose substitute five of my six planned meals. The upside is though that if they front-load your meat/prepped veg/ready-to-cooks etc so it won't last you through the week, they'll just give that to you free.
Also my delivery chap is rather nice. 