I don't know if anyone has seen this site, but I find it really useful.Log In compares prices across most UK supermarkets so you can cross-check prices without having to go to all the stores yourself. It's normally pretty up to date on deals, even if it doesn't have every supermarket only most of them. I certainly saved time and money by using it.
This looks something really practical which is immensely helpful for the customers. To my knowledge, there's no site here where we can make this comparative study. And when most of the e-stores are introducing app based usage, it becomes even more difficult to compare the deals among the businesses.