Ok, first to set the scene........

"wooden" conservatory which is of a lean to shape, the box shaped bit
is mostly large DG wooden framed doors , the roof is twinwall polycarb
and the triangular panels which make the infill between the top of the
glass box and the roof at the sides are wooden frame with T&G on either
side.

The T&G is needing replacing and we'd like to add some ventilation.
The conservatory gets very hot if it's left shut up, and the only way
to provide ventilation at the moment is to open the doors. Not
convenient when we're out.

Any suggestions for the best material to use on the outside, and what
sort of ventilation to go for (or indeed if you think ventilation in
these end panels isn't going to be effective).