Sheep are awesome. Go for it!
. 1000m2 should be enough for a few primitives for most of the year if you manage the grass well (I would suggest getting a couple of *self-shedding* Castlemilk Moorits which are docile, only need rooing and are beautiful- or probably even a bit better a couple of Soays which are smaller but a bit more 'jumpy').
A few things I would do to give you the best chance of success to add to the other advice-
1) before getting them allow everything to get really overgrown (primitives will take down really tall and overgrown areas).
2) sort out gaps etc in fences
3) Strike some fast-growing willows in a sheep proof area- maybe a new hedge? (so you can cut as browse which will help supplement your feed in summer and winter).
4) Buy a good hay feeder and get a supply of really top quality hay to feed ad-lib. Get the 4ft version of this
https://iae.co.uk/product-agriculture/sheep-hayrack-on-wheels/5) Buy lots of hurdles so you have full control of where the sheep graze. You should graze an area really hard and supplement with ad-lib hay, mineral lick and energy lick
http://www.molevalleyfarmers.com/mvf/store/products/mvf-mole-lyx-sheep-salt-elite-20kg-pack-of-2;jsessionid=1B9A42079D174593209D1A470872D7D1. Once that area is done then move them to a new area and move the hay rack and lick with them.
6) See if you can find 'respite care' for them if your land really won't take them over the winter (my friend
does similar to what you are proposing and I have occasionally housed his sheep over the worst of the winter months).7) Keep a daily eye on them to see that they are thriving- and if unsure get a trusted farmer or vet to advise you (or get advice off here).
During summer this will prob work OK. As you hit winter it may be that you need to confine the sheep to a hard, dry area (and with shelter with a covering of straw) until your grass starts growing again. Don't ever allow them to get muddy feet. In a small area you would also be advised to remove droppings. Feeding will never be a problem- just feed them ad-lib hay from your feeder (and a handful of beet shreds- which are a by-product of the UK sugar beet industry so environmentally much better than soya products, some clippings from your willow or even offer a few fodder beets).
Best of luck!