The only natural pet foods that we have been able to find here in the UK that might meet your requirements are Orijen, Arcana (both Champion products from Canada) or maybe Taste of the Wild. One of my ridgies is elderly and full of lumps and bumps, so we keep him on a grain free, lower carb food and my other ridgie has a pretty sensitive stomach and does better with food from bison, venison or fish protein sources.
We had absolutely no luck at the larger 'chain' pet shops, but found two local shops and a vet's practice that carry natural pet foods. One of them even delivers!
I'm in Surrey, so don't know if this info will help you, but I'll share the links anyway.
http://www.dolittlepetsupplies.co.uk/http://www.weybridgepetcentre.co.uk/The owners and staff at both places have been really helpful and they were happy to try and find a supplier for any food that I was interested in. (we mostly feed Orijen right now)
Hope that helps.
