I've been and placed a special order for the new plastic for the hatch top.
The old one, upon measuring was 12mm thick, and with advice from the provider, I have replaced it with 12mm Polycarbonate, which will be bullet proof.
I could have gone for Acrylic, but the advice was that it would flex too much and not be safe when jumped upon. I suspect this was a little overplayed, but the hatch is horizontal, and on the foredeck, and could therefore face several tons of water being dumped upon it, so it can't be too strong!
I haven't also been able to source smoked Polycarbonate in that thickness, so it mean that the new material is clear.. I ummed and arred about this for a while, concerned about temperatures down below, but decided that i'd rather have thick and strong, than thin and smoked.
I can always put the cover over it if it starts to get too hot in the interior.
So, the flip side of the wood part of the hatch has now had its first coat... onwards and upwards!