Delayed update: I have now used a combo of black silage wrap between willow rows with newspaper for the gaps along the rows, simply weighted down with a very bountiful supply of stones that ploughing and harrowing has eventually produced !! The ground is sloping, so the rows will receive good run off of rain, but I've also punctured the wrap where each stone is placed to ensure inter-row penetration aswell. The grass is resilient: while the silage wrap is not totally opaque, I'm v surprised that it still looks like a buttoned mattress so many weeks later!
I have rabbits and roe deer living on or frequenting my bit: the bunnies were onto the willow cuttings in a flash. Quick erection of rabbit netting simply staked with bamboo canes nipped that in the bud (pun intended). As it is a very temporary arrangement, I merely strung 2 runs of fishing line above after experimenting with some fishing line 'barriers' across field openings and across the tops of stone walls where deer obviously cross. Judging by the 'confused' hoof marks in the mud, they didn't like it one little bit (although a couple of attempts were obviously made to jump the 'invisible barriers' because the top line was broken a couple of times)! So far, definately no rabbit and seemingly no deer intrusions into the fenced willow planting.
Permanent rabbit/deer fencing to 5 acres is next 'project'. Some fencing experimentation will be involved and a trial selection of components has been accumulated (including the Screwfix bundle of Tornado's premium rabbit netting - great price). I'll report idc!