4. Swap tiers rather than swapping items
Most supermarkets stock three or four tiers of the same product: a budget line, an own-brand standard line, an own-brand premium line, and the national brand. The price gap between the budget line and the brand is often two to three times, and the quality gap is usually far narrower than that — sometimes nonexistent, because the same factories produce several tiers.
The efficient move is to drop one tier at a time across a whole shop rather than agonising over individual products. Drop the entire list one tier, use it for a fortnight, and note the three or four items where the difference genuinely bothered someone in the house. Move those back up. Everything else stays down permanently.
Some categories reward this more than others. Flour, sugar, dried pasta, rice, oats, tinned pulses, frozen vegetables, cleaning products and bin bags are close to identical across tiers. Coffee, chocolate, cheese, bacon, ketchup, mayonnaise and washing powder are where people most often notice and switch back.
Frozen vegetables deserve a specific mention. They are picked and frozen within hours, cost a fraction of fresh, and do not spoil in the drawer while you fail to use them. For anything that ends up cooked — peas, spinach, sweetcorn, green beans, berries in porridge — frozen is usually both cheaper and better, and it removes a whole category from the waste column.
Meat is the biggest single lever in most trolleys. Cheaper cuts cooked slowly — shoulder, thigh, shin, brisket — cost half as much as the quick-cooking cuts and reward a slow cooker that runs for pennies.