i'm getting new trims and could't be bothered to take that bit of trim off to do the job LOL.
the car was rusting inside out. turns out the whole panel is rusted from top to bottom due to broken seal on the roof and a rusty hole under the seal, making my boot wet and my back seats. so i used unibond sealant under the seal on the roof and stuck it down. then fixed the hole at the bottom.