Right Bill,
with acres per sheep it depends on,
Size of the breed ( you could accommodate more Rryelands per acre (3)than you could Suffolks or Texels)
Whether they are expected to sustain themselves on the pasture or not ( so bottle fed lambs or heavily pregnant ewes eating hay and hard feed will tend to hang about the feed source and not take advantage of large areas of bald pasture.)
The quality of the pasture in relation to their needs ( if this is their only source )
So, if you using rolls of 50mtr netting then I would suggest using 4 to create a square paddock as a starting point with access to fresh water. Assuming that you have lots of lovely sweet grass flushing through from mid April them they are going to have plenty of pasture to meet their needs to meet their needs and as young lambs they will tend to graze close to each other so will have enough personal space too.
See how they get on for a few weeks then adjust accordingly. Under-stocking is always better than overstocking though. However, people who strip graze often confine their stock to areas much smaller than recommended but move the fencing a few feet further each day to offer fresh grass and encourage the sheep to graze the pasture more intensively. This method can also be effective.
Hope that helps,