Sounds perfect. Buy some store lambs, fatten them up, get them in the freezer.
6 to 8 sounds fine on what land you have as you'll probably be wanting to feed them that little bit more in the last few weeks anyway with pellets and that.
I would make sure they have been wormed some time in advance and would monitor them for signs of worms up till slaughter time so you can treat them if they do get signs in the meantime. - Cant advise borrowing a small amount of wormer from a neighbour if they do show signs of worms as it against some rule somewhere. - But best to keep them without worms, this is both for important for them and for you, the end consumer in the end.
As far as I know you will also need a holding number and a few other bit of paperwork like transfer/transport details and medical records.
-Maybe someone else can tell us how many sheep you have to have before having these documents?
Ta
Baz