Thanks for the tip about Wolsingham - after a little Googling I think that must be David Pike at Heartwell Farm.
A little further research on TAS seems to show that the user "arborexplora" might be the one for Saddlebacks in County Durham
So long as they're in the general area of the North Pennines then that's good enough for me. The main concern in my mind would have to be the travel time/distance for transporting livestock.