Help, water in rear wing

UK 1997 1.8

I noticed some paint bubbles in the passenger sill area. Fortunately it
was to the rear of the seam where the rear wing joins.

I removed the rust and found that the sill was still OK underneath and
it was the wing that had rusted though. I have rustproofed, filled and
painted the wing but I want to stop the water ingress. The driver's
side seems fine.

Any ideas? The hood has seen better days. If I got someone to fit a new
hood, is this something they could solve?

Thanks