Phone the local abattoir's and ask them about tripe, chicken and mince if they say they dont know they cant be bothered to find out so ask nicely they sould be able to put you on to someone, they souldn't sell it themselfs, but who no's. You will need to buy bulk to get a decent price but any where between 20p-30p/lb for tripe, chicken a little dearer and I am not sure about mince. Good luck.