Hi there!
Not sure why we hadn't seen your post and said Hi before this, sorry 'bout that. We are usually a pretty welcoming bunch!
I used to be north of Hadrian's Wall myself, and loved driving southeast across the tops to Weardale and places. So I can imagine the type of ground it is.
Down here we talk sheep/acre, up there it's acres/sheep
So one thing your 4 acres could do is be a bit of extra summer grazing for one of your neighbours. A few ewes and lambs in summer, maybe. And / or perhaps somewhere to keep a few tups in winter after they've finished their work.
But if you want your own livestock, then the simplest thing would be to buy a few weaned lambs off a neighbour each year and fatten them up. Or even get into having a few orphan lambs and rearing them yourself, but it's always a good idea to learn a bit about keeping lambs by getting some weaned ones the first time.
Did you have any ideas yourself? Anything you have had a hankering for?