Ok, so made my own now. 12mm MDF, but what a b*itch to get fitted properly. A couple of hours with a jig saw and surform and much swearing. Mind you it only cost £15 all up
The top edge sits just in front of the cargo net hooks with the bottom about 3 inches in from the front-side of the arch so it isn't quite vertical. Scuffed the nasty cheap plastic material in the boot quite a bit fitting it, but it looks ok.
Chose to cover it with black leatherette from the local haberdashery and used spray glue to avoid any nasty staples. Didn't put any rubber strip on the edges and the material blends in quite well with the plastic boot lining material.
If I can find a way to get the shape imported and measured in to Visio I'll post a dimensioned picture.
Hooray ! £30k car with a £15 tonneau cover