Thanks to everyone involved,
Hmmm now how does this work? Buffalo Bill and I had a go at setting it up tonight in my dining room (2 anchor bolts in the walls while she was away) after a lot of head scratching off down B&Q to get some bungees 2 x 90cm. This is what we tried. Where the rope goes into the hammock we put a small loop of Para cord and put the bungee through, attaching them to the outer loops on the under blanket, same on the other end. This looked good with the 2 side toggles lining up with the bungees on the Hennessey hammocks and enough freedom for movement. We put a figure of 8 loop in the black bungee cord on the under blanket pulled these tightish and put them up to the Para cord loop pulling the head end tight. The entrance end of the hammock Im still lost with whats best to do? I couldnt open the hammock out fully with the tarp on as not enough space. So still a bit of fine tuning left to do, but these are my initial findings I hope it helps. I will take some photos when we go out on the 17th Nov and give a review.