I was going to say Shetlands too, but they are not particularly big. For a larger carcass and a truly beautiful rug, how about Jacobs? They are perfectly hardy although many breeders mollycoddle them to get them to breed at Christmas, good mothers, have triplets often and can count to three (so you don't need to take the third lamb off them), go for slaughter in November at 7 months so their skins are fine to process before the winter wool break, and the skins can sell at a premium if you have a well-marked flock. And as a final plus, their fleece, if carefully bred and selected, is highly desirable to craft workers such as spinners and felters. Who could ask for more?!