My boot gets a bit of water in after heavy rain, need to sort it but the weather needs to get better before I can!
Three likely areas - Boot seal, which I intend to pull off, reseal with some sticky silicone and replace. Rear light clusters have sealant around them where they attach to the body, not sure this is the issue with mine but will redo since I'll have the sticky stuff to hand and finally the spoiler bolts which I think is going to mean taking the spoiler off and giving the holes on the top side of the boot lid a blob of sticky silicone. Really hard to tell which is causing the problem, so I'm going to address all three. belt and braces!
I've read the best stuff to use is non-setting silicone but since I can't do the job til it stops raining every other day, I've not bought any yet! I've taken the carpet and liner out for now so it doesn't start to smell