When we take our BF tup out he has to be put in a block and tin shed, with sheep hurdles tied vertically across the stock gate at the front. That makes it at least 6ft high on every side - the only thing that'll hold him.
Time of year ewes cycle may depend on whre you are in the country. They begin as the days shorten, which means lambing will coincide with grass growth in Spring (well, apart from the Poll Dorset, which seems to have a calendar all of its own). I have a ram lamb out on loan at present, but certainly wouldn't be wanting to lamb in early Summer myself - too many flies, for a start.