Bodywork materials

I'm currently half way through a major autumn clean / polish /wax on our 'van and am wondering on the actual materials of individual panels.
The roof, overcab moulding, cab-to-side panel mouldings and side skirts all seem made of the same material, which has more a plastic finish.
The side panels themselves appear to be much more solid but don't seem to be the same as the moulded panels.
I'm just wondering if they are all classed as GRP.
In addition, the bumpers seem to be what I'd call proper fibreglass.

Incidentally, I have just finished off my supply of Meguiars 50 Marine / RV Cleaner Was One Step on the roof, (which I've previously used for all surfaces). On the overcab section I've gone over with 56 Pure Wax and it's come up gleaming and shiny.

However, the side panels never come up as good, so I've bought Meguiars 49 Marine / RV Oxidation remover for those panels and am going to finish with Meguiars 56 Marine / RV Pure Wax.

It'll take another couple of days to finish but should look good by then (I hope).

nuevoboy (with the aching arms).

If you have any left ( energy, polish, cloths) I have a Broadway that needs a polish!
As far as I know, mine if GRP all over ( except the cab) but with different top coat finishes. The side skirts though are painted aluminium. I use Meguiars Gold Class car shampoo and Autoglym resin polish on everything.