If you want to help the British sheep industry, and you’re looking at those sorts of quantities (lorryloads), you could use Mule. She’s the daughter of a Blue-faced Leicester tup on a hill or mountain sheep, and her wool is wonderful, very versatile - and plentiful! You could buy bales direct from BWMB, at their prices, which would leave you a bit of leeway to pay for processing and make a profit. There are regional variants too - Scotch Mule, North of England Mule, Welsh Mule, Exmoor Mule, and so on. And the dad being Blue-faced
Leicester might hit your need for a locale-related wool?
If you’re doing hundreds of kilos at a time, you could use the likes of John Arbon for processing. Or maybe even the Curtis empire. I don’t know who else operates at that volume level.
If you’re looking at starting smaller, with 20 sheep of your own, you’d be just about getting enough each year for the likes of Natural Fibre Company (min 20kgs fleece per batch for yarn). Or Halifax Spinning Mill (not in Halifax), who will go down to one fleece to help you get started. One piece of advice would be to skirt the fleeces very hard and only send the very best fibre. Incorporating even only a bit of harsher britch wool would have a seriously negative impact on the handle of the final yarn.
If you prefer one of the rarer breeds, two that could be worth exploring would be Whitefaced Woodland and Derbyshire Gritstone. Both a little north of Leicester, but not a gazillion miles away. Both have surprisingly lovely fleece, good for jumpers, cabling, etc.
Other rare breeds which produce good wool for jumpers include Portland, Oxford Down, Devon Closewool, Llanwenog, Norfolk Horn, of which Oxford Down do come in coloured as well as white. Equally good, and native but not classified as rare by the RBST, are Romney, Ryeland, Dorset Down, Shetland, Shropshire, of which Romney, Shetland and Ryeland come in colours as well as white. Not native nor rare but so prevalent here for so long it’s almost naturalised, and with good colours which would aid with making tweed fabrics, would be Jacob. (Those lists aren’t exhaustive, but I haven’t included any breeds whose wool I haven’t experienced, or whose fleece I have personally felt was not suited to jumpers.)
Tweed is dyed and woven, and traditionally would be the wool of the local hill and upland sheep. There’s a woman in Cumbria making a big thing of making tweed from Rough Fell. Rough Fell is a seriously harsh fleece, so it’s a hard-wearing outer fabric she’s making. Shetland, although a soft, fine fleece, makes an excellent tweed, as you have the natural colours to help give the “tweedy” effect, plus the woven fabric fulls to make a nearly water and weatherproof fabric. Maybe not the most hardwearing though - but much softer than the Rough Fell one would be.
Give me even a tiny bit of encouragement and I will go on some more