Aldi or Lidl.
Drop meat and fish - you don’t need it. Protein is found in so many other foods.
Plan meals around things that are on special offer.
Stock up on special offer items and freeze them.
Find out what time the reduced items get put out and pounce!
If you buy packs of nuts/dried fruit, buy the bigger bakery packs and portion them up.
Meal plan - make a list and stick to it - no compulsive shopping.
Don’t buy ready sauces and ready meals. Make everything fresh from scratch and in large quantities and freeze it.
Nothing wrong with Aldi’s cheapest pasta, rice and spaghetti. Cheap tinned tomatoes also good.
Nothing wrong with simpler, cheaper meals like baked potato with cheese and salad or beans on toast a couple of times a week.
If you have a garden, start growing your own veg next summer. Start with the easy things like lettuce, tomatoes and radishes. Runner beans are the best home grown.