If the meat is for yourselves and friends, you really don't need to be thinking about a commercial animal, except from the point of view of not keeping lambs on over winter. The taste of at least two of your suggestions is orders of magnitude better than any commercial I have tasted, and at least one of those will mature in one season.
You don't say what type are the sheep they will be joining?
Sheep can be very racist (!), and stick to the pals they know, and newcomers may not be fully integrated until after next lambing.
Which aside, they will integrate in time because they will get used to each other and because 4 is the minimum size for them to feel like a flock.
Zwartbles are huge, very friendly - over-friendly for some; pushy and have no fear of humans. Mostly the fleece is not very exciting for spinners, but they do have their fans, not least because of the strong solid black colour which is quite rare in sheep. Feet can be an issue, take someone knowledgeable with you to buy and look at the feet of the rest of the flock if you can

. Some Zwarts seem prone to flystrike, but some seem to be quite resistant. Meat tastes excellent and you can put a Zwart ewe to pretty much any tup and she will have the lambs away before winter. Joints are a bit large for some households; we love them here, but we are cooking for 15-25 at a time! A whole leg feeds us all

Zwarts might need cake over winter and while rearing lambs; it was a dairy breed so they produce a lot of milk, but need plenty of input to do so. That's what makes the lambs ready before winter, but if your other sheep don't need feed / tend to fat, that could give you management problems.

I know very little about Cotswolds except they are quite large and very woolly! Some have fab wool and spinners will pay a lot for fleeces, but unless you know something about it you are likely to end up with sheep whose fleeces are at the rougher end of the longwool spectrum, and are not particularly sought after.
Longwools can need quite a bit of extra care, especially if your ground is muddy in winter, and they may need very careful management to avoid flystrike.
I have had a couple of Wensleydales and I would expect Cotswolds to be somewhat similar to manage. Wenseys can be rather lazy mums, might need a nudge to get on and clean and feed the lambs, my one had a single every year except her last (and we then discovered half her udder didn't work, sigh), and she and her offspring are quite prone to getting mucky and needing dagging, and to flystrike if not kept clean. But... big lambs, ready for the off before Christmas. My "one-half" Wensey has the most amazing steely blue lustrous fleece, and I forgive her a lot of extra work for the quality of that.

I have had a lot of experience of a lot of different sheep, and I have said many times that if I had only shepherding to consider, I would choose pure Shetland every single time. Lambs squirt out running, straight to the milk bar, mothers know what to do, (main piece of lambing equipment is a pair of binoculars, just leave her to it), fabulous little sheep. Usually good feet, meat tastes amazing. Some Shetland fleeces can be a bit ordinary, but if fleece is of interest you should have no trouble finding sheep with really nice fleece.
Big downside is they aren't huge sheep and if you don't want to be keeping them over winter the lambs would be even smaller. We get some of ours away before Christmas but the majority of pure Shetland benefit from being at least 12 months old. We don't cake, mind, we find the meat is best on pure grass.
Shetlands can take a larger tup but I would breed pure the first once or twice, and you'd need to go back to pure after say 3 larger crops as the belly muscles start to sag.
Tell us more about the two they would be joining?