I'm all for the old breeds, and slow matured grass-fed mutton - but I do have to say that spring Charollais lamb is as sweet, succulent and tasty as you could ever wish.
And I also agree that it's a fab sheep for crossing - easy lambing, lively lambs full of get-up-and-go, grow well, always weigh more than they look. Only one problem really, they can have such a thin fleece the lambs may be almost bare, so jackets may be needed in wet weather.