Thanks - I've only got 14 at the moment, 3 old pet ewes and 11 hoggs. I don't really want to split the hoggs up, I don't want to put the 3 older ones out on the hill on their own, but they're completely unafraid of dogs and not suitable for training on!
The other plus point for keeping them in is nettle and dock control, but the 3 older ones got fat on the fields over the summer without being fed at all, and that was with the horses in with them helping keep it down. I guess having another 11 will solve that one though!