100m rolls are very heavy, so bear that in mind. If your terrain is rough then stick with 50m rolls, even though it is cheaper to buy 100m rolls. You don't need to use gripples to join rolls together. Do some googling, there are a number of wire knots you can use, like this guy:
https://www.youtube.com/watch?v=71YHr-v9vSEIf you have left over stock netting don't worry, you'll find a use for it eventually
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As for suppliers, any local agri store or fencing place should stock stock-netting. Tornado is a popular make. C8/80/15 is the correct size for what you need.