If you want Shetlands buy them from the Island, much better sheep, make a good cross with the Cheviot, think @scholland has someI don't know much about them, except that seeing as they've been popular with the smallholders -none intended- the selection criteria will have been down the toilet for years.
(in fact, do I recall aficionados breed certain colours?)
Subsequently wouldn't want unless they were a last resort
(says a man who keeps funny coloured cattle....)