Thanks for all the suggestions.
Have now had chance to take a closer look. The 8m x 10m top is trashed. Many of the eyelets pulled out. Notice that the listing says that they are not covered by any warranty. Now there's a surprise. One of the bottom side ones has also had its eyelets ripped out at the bottom but I can live with that.
Having come this far and bearing in mid that the wood OSB is too damp to do anything with until it dries ...so no varnishing etc .... and that I reckon cocooning it in plastic is going to be a recipe for disaster as it's wet now, I'll have one last try and get an even more heavy duty tarpaulin for the roof.
I had thought about something like a cargo net but do recall not having much success as to size. But will revisit. I may well jury rig something up as I have scaffold tubes in the right place to do this and a huge drum of blue cord left (I bought a 500m drum for this project
)
I'm also thinking that the top will have one end unfastened so that any wind has somewhere to escape from hence reduce the loading.
Just damn glad I brought all my tools in before I went away.
If opportunity doesn't knock, build a door.