The 'Lid'.
I had two 3m lengths of 1/2" galvanised pipe onto which I put 4 off, 5/8" 90 degree bends, one at each end. Inbetween I slid on 5/8" 'T' pipe fittings. Between the 'T' fittings I put lengths of 5/8" H/d plastic pipe cut to about 40cm length. The plastic pipe held the fittings at the right distances. I put each loosly assembled 'rod' onto the angle iron brackets and loosly tied them on with string. The supports which formed the roof were made from about 7off 3m lengths of 1/2" semi-rigid plastic tube.
All I had to do was push fit these tubes into the pipe fittings. The tension of the bend was enough to hold them in place. Just before, and during this bit of the assembly, I applied silicone glue/sealant to all the 'joints' and gaps including where tubes fitted int the pipe fittings.
While the sealant was setting I put gaffers tape between adjacent roof tubes using a piece of wood with two nails hammered in as a spacer. I fastened the long bottom 'rods' to the angle iron with twisted wire.