Damp proofing

Any body got or heard of anything to apply to underside of metal roof skin to stop moisture building up and causing head lining to go all soggy and damp?
Took mine out today to clean it and the ammount of condensation on roof was quite phenominal, its also causing headlining to go black wi damp which is not good
I heard of something years ago you could paint on and it stopped the condensation, dont wanna cut roof and put in one of those vent thingys coz they look daft spinnin round on your roof.
Any help or suggestions guys?

I've heard of people using old carpet or underlay stuck to the metal with spray glue - anything to add a bit of insulation and also increase the surface area for evaporation i think.

Theres a small bag you can buy and leave it in yer landy. Stops condensation apparently - it was touted in all the Landy mags a few months ago. When it "fills up" put it on a radiator and dry it out, then repeat.

Or a bag of salt.

Been out today and sealed up leaks round rear windows and alpine lights, just gotta get black sealer and seal round where rear tub meets side panels as the rubberr seal is perished and nasty, hopefully this will also help.
Gonna pva bond the back sides of roof linings to,
Will let you all know how it goes

Well thats the tub the windows and the roof sealed and even fitted new rear washer jet so jus need some rain now to see if anythin else leaks in the back before i put the headlining back in, fingers crossed and all that