I'm reluctantly posting this hack, its not a 100% solution.

I have a leak in my windscreen seal. The van came with evidence of
some sealant around the edge between body and rubber, and this last
summer I tried adding a bit more. But when van is parked during a
heavy overnight rainstorm, there is still a bit of water collecting
inside on forward part of dash, righthand side.

I know I have to pull the glass and do it right. But meanwhile...
using the straw on the aerosol can of fluid film, I sprayed around the
outside edge where it meets the body. All along the top edge and the
sides especially.

Well it seems to have helped. I'm guessing the waxy hydrophobic nature
of the FF is forming a bit of a barrier to water. Its not a perm. fix,
but its working so far.

alistair