Buy a book called Give Your Dog A Bone by Dr Ian Billinghurst - he's like the BARF guru - the book is brilliant - its written in plain English so you can understand what to feed and why you feed it
The frozen Tripe from Landywoods comes in 1 lb packs and its 26p - I know when I only had Nelson I used to buy it from jolleys and it was about 60p - self same thing so its alot cheaper than in the shops.