My FIL weighs those packs of chedder cheese and chooses the heaviest -those ones where they have a fixed price and supposedly same weight.
They actually vary by quite a bit.
In regards to 3 for 2 and 2 for £5 etc, I prefer Lidl and Aldi -they hardly do these multibuys.
And they have the 'middle aisle' -alleviates the boredom of food shopping. Its amazing how many tools you dont have a use for, you can end up buying, just because its cheap .