Clarebelle,
I have no specific experience of keeping sheep, as we ourselves are just starting out with sheep. However, Rosemary herself (the accidental smallholder) suggests the following:
"For guidance, work on 3-4 ewes per acre, up to six on good, fertile grassland, fewer on less productive grass. You will also have to take into account the needs of other grazing livestock, including poultry. And large breeds, raising twin lambs, will need more grazing than a small ewe with a single lamb.
There is more information about stocking rates in the guide on
Grassland Management. The most important thing is not to overstock or your grassland may become damaged by poaching and infested with parasites."
We're kinda working on these stocking density levels...
Lynn