I shop at Sainsburys where I can. The main supermarkets for me are Morrison and kind of forced to use M&S.
Everyone has their super market preference. ASDA would be cheaper still. You can't disagree that prices have sky rocketed, shrunk in quantity and now lower quality.
I am not denying there is inflation and shrinkflation. However I kept my bill in check by doing the bulk of my shopping and cheaper stores e.g. Aldi (quality of most stuff is comparable to more expensive super market) and only spending more when it makes sense.
The vast majority of the public doesn't understand what causes inflation or that there is a difference between monetary and price inflation and energy is part of that.