What's the best cheapest food I can buy?

I'm currently spending £25 on Zeus' 15KG bags of Bakers Complete and £13 on Milo's 6kg bags of Bakers Puppy..

Yes I know Bakers are not looked at greatly on here, so I turn to you for some help.

Also my local vet says since Milo is the working type of Labrador I don't have to pay VAT on his food?

So erm... would telling you their size be any use?

Zeus is 3 years old and weighs in the region of 4-5stone.
Milo is 4months old and weighs 2stone 13lbs.

Zeus is a boxer cross, and Milo is a pure Labrador, if that helps?

So please, tell me the best cheap food that I can get.

Has anyone tried Wainwright's dry dog food?