I buy all my feed from "Davidson's" in Blairgowrie. I have shopped around and they are cheaper with most the things I buy, and I buy a fair bit. They deliver to me, but not sure if they would to you but you can only ask. Their number is 01250 874486, failing that you have Carrs Billington in Milnathort which is closer than Dalkeith for you.
Hope this helps.