Thanks all. My seemingly silly question has thrown up some very valid aspects I hadn't thought of, so I'm glad I asked (even tho I might appear a bit dim when it comes to my overcautiousness with my new flock).
Before seeing all the replies I'd put them
all together, into the field which I had separated the new mums and lambs (2 weeks old) into (just one ewe left to lamb). Hope I've done the right thing...........
I have a v small flock (all meds, [and feet] up to date and none due for attention yet).
As usual, all advice greatfully received.