Which part of Cornwall? We have (at least) two very distinct weather patterns... I'm on a near-coastal hilltop in North Cornwall, it's more like Exmoor here at times! My pal near Calstock wear shorts all summer, mine don't get nearly as much use as hers!
If your weather is more clement than mine, you might want to look at Wiltshire Horns. Most of the allegedly self-shearing primitives don't
reliably shed, so if you really want to not shear at all, I think it's Wiltshires or Soays. My understanding is that Soays can be very tame but can also be wild as a bag of cats, and are not very flock-y. So if going that way, make sure you
see the flock they're from being tame...

Wiltshires aren't exactly labradors either but do properly self-shed.
Both sexes are horned in both those breeds.
If you can bear to shear, kids love Shetlands with all their lovely colours, pretty faces and quirky personalities. Again, make sure you are sourcing from a flock you have
seen being very tame. Our ram is polled; they do occur, but most Shetland rams are horned. Ewes are polled, however.
I've said so many times that regulars will be yawning... I've experienced a
huge variety of breeds and types of sheep, and if I only had myself to please I'd go pure Shetland every time, based on what's easiest for the shepherd.