OK head lining up date.
Once the hardboard base was out the worst job was to remove all the old glue and disintegrated foam sticking to it. Using brush on glue, NOT spray glue, it was quite simple to stick new material on the base. Putting it back in the car was childishly simple, just bend the middle down, the sides up and it literally springs back into place, having used the old piece of material as a pattern there was a strip hanging down over the top of the rear window rubber, which simply tucks in behind it.