leaking boot how can i fix it?

i have a vauxhall astra life 1.8 auto on a 56 plate and just lately i am getting water coming out of the plastic trim around the boot on the right hand side of the car. The water is not getting in to the boot or on the carpet but still would like to get this fixed before the small problem becomes big. Have checked the boot rubber and rubber around window and they both seem find but any advice would be great