I think it very much depends on where you live as to where you shop, how much time you have and whether you have a car or not.
I have lived all over the place and generally speaking there are more Tescos around than anything else.
I have attempted to shop at various Aldis/Lidls etc. over the years but generally give up as the shoppers look like prison convicts/hardcore thugs/the depressed and the weary and it just demoralises me!
Tesco is generally pretty affordable as it keeps competitive like anywhere else.
I would just like to say I miss Waitrose now I have left London sniff, it was great popping in there for a handful of foods but I hope one day to bump into one again even though I am living in the midlands!
Night x