Shetland or similar. Buy from the right breeder so they’re tame ones. Great feet, no lambing issues, amazing hogget - full of flavour, succulent but not fat, fantastic fleeces for spinning and skins to sell in addition to meat. (Processing costs around £30-£35 per skin, but a nice coloured sheepskin will sell for £50-75. Good fleeces will fetch £8-20 depending on colour and quality.)
Shouldn’t be too difficult to find rams locally so you don’t have to keep one if you don’t want to. (Could be a bigger issue with a rarer breed.).
Slaughter and butchery costs are at least partly per animal, though, so the smaller bodies of this type of sheep mean the cost per kilo is slightly greater. And of course you’d keep most or all through two summers, meaning you have lambs staying through the winter. If the ground is wet, you might prefer a larger breed where most of the lambs are away before winter. Less fleeces, but you can still do the skins, and you have less work and costs over winter.
Of the breeds your list, I’ve not specifically tasted any, so can’t comment except to say (a) I agree that most non-commercial grass reared sheep meat tastes fabulous, but the Northern Short-tailed type (of which Shetland is one) have a depth of flavour all their own, ime, and (b) think about flies; if your land is both wet and sheltered, so not breezy and airy, you may well do better with something less woolly, like your suggested Wiltshire Horns.
If the idea of selling / using fleeces and skins appeals, then Wiltshire Horn would not be the best choice! Lol.
Re-reading your post, the Shetland and Manx I’ve eaten has the depth of flavour heading towards the gamey end, but without being actually gamey. Castlemilk Moorit has meat in a class of its own, incredibly lean, definitely unlike other lamb. Some say it’s almost like venison, but it’s nicer than some venison
I’ve found that most people who like lamb do like Castlemilk Moorit, and most people who *don’t* like lamb, also like Castlemilk Moorit.
You’d need to source carefully, though, to be sure you got tame sheep that would be successful breeders of tame sheep
. Gorgeous to see a flock of these elegant sheep <3