I'm about to clad the fascia boards on my house with UPVC fascia cladding
(10mm thick). The existing wooden fascia boards have a little wet rot in a
couple of places. So I'm thinking of treating those sections with some kind
of wood presevative prior to nailing the cladding in place. I just want to
make sure I don't use a preservative that's going to exude chemicals that
could affect the UPVC in any way. Any suggestions?

I would replace the affected woodwork, but there is no way I can do this as
I can't afford a scaffolding and am doing the job with a ladder only.

I'm wopndering if it's even necessary to treat the affected fascias,
because wet rot stops as soon as the wood is no longer subject to dampness,
I gather. Any views?

Al