Where is the cheapest place to buy the big tin of Pedigree dog food in the UK?

The big yellow tin of Pedigree chum dog food is pretty expensive, especially with a big dog. Where is the cheapest place to buy it and how much does it cost. Also, does anyone no if this is the best, or a good dog food for your dog? Any other brands and the prices will be much appreciated, thanks :). And don;t think im being stingey lol, i will pay the the price for my dog no matter how much, but if im buying one brand obviously i want to no the best price. Oh yeah, and ae the expensive brands better then the cheap ones or supermarket own brand ones? Im done haha! Thanks