UK & Ireland Distributors of ORIJEN, ACANA, ZiwiPeak and Purr & Simple | Bern Pet Foods you can get Acana and Orijen on this link.
You can get Fromm here
http://www.postalpetsproducts.co.uk/index.asp
I have not found anywhere selling Canine Caviar here yet but will let you know if I do.
You can get Royal Canin breed specific for yorkies in pets at home.
Hope you get something that suits your sweeties