Wooden Bay - need to insulate

[XrayDave]

Hi,

I have a 2-storey wooden bay window with exterior overlapped cedar cladding.

I suspect that there is little (or no) insulation between the exterior cladding and the internal plasterboard although there is a waterproof membrane.

Any idea where I can get dark "wood effect" uPVC cladding so that I can take the cedar cladding off without worrying about damaging it?

I presume that this type of cladding is hollow? If so, is there any that has any internal insulation?

Suppliers in S.Yorkshire area please.

Thanks in anticipation.

Dave