Black Welsh Mountain for easy to keep, hardy, good milky mothers, will eat anything, very tasty to eat, handsome to look at sheep. And there are plenty available in Wales. You could also cross them with a beefier meat breed ram if you needed bigger lambs.
Otherwise I'd go with Lleyn, or easy care.
Whatever you pick, try to get some from someone who has similar land to you, that way you know that they will do well at your place.