Some other Welsh breeds that I know something about. (There are more, but I know nothing at all about breeds such as Clun Forest, South Wales Mountain, Hill Radnor. Have a look at the RBST website for more info about the rarest.)
Badger-faced Welsh Mountain sheep, Torddu. From what I hear (but people always overstate the strengths and avoid mentioning the downsides of their own favourites...), they seem to have many of the attributes of the Shetland (which is the breed I would keep if I had to choose just one, and had only myself to consider.) Torddu has lovely fleece for crafting.
Badger-faced Welsh Mountain sheep, Torwen. Supposedly the "photographic negative" of the Torddu. But as populations are bred, they diverge, so they may or may not have the same attributes as the Torddu. The one Torwen fleece I've had wasn't a joy to handle or spin but I'd hesitate to damn the whole breed on that one example, particularly as I don't know who the sheepkeeper was, and whether they know anything about fleece for crafting. (We acquired some through the Rare Breeds network for the first Tour of British Fleece in 2015. Torwen was one of the most difficult to get hold of, and we don't know the origin of the one we eventually got.)
Lleyns are now used commercially, particularly in organic / grass-fed systems, so should be fairly plentiful across the region. Excellent lambing and mothering (but can have a propensity to triplets), do well on grass only (even rearing triplets if on good grass), quiet / not flighty. Nice enough fleece for crafting (but not particularly sought-after as quite plentiful.) From my own experience with Lleyns, feet ok but not in the same league as some of the primitives, some propensity to flystrike.
Beulah speckled-faced. I know very little about these sheep, but the fleece we had was one of the most delicious of all the Welsh fleeces we had (for the Tour of British Fleece.)
Kerry Hill. Striking-looking sheep, have quite a few devotees - and not just in Wales. I've had only 1 fleece, and I know it came from someone with no knowledge of fleece, so it could have been a particularly poor example - but it was horrible!
Black Welsh Mountain. I believe (but not firsthand) that these are generally good hardy sheep, suited to outdoor lambing, decent feet, and good meat. Probably not particularly tame though. I've had one very delicious fleece, but I know that the majority will not be of that quality, and the fleece is not particularly popular with crafters.