citroen berlingo wet foot well /water in rear underfloor stores?

recentley got a 2000 reg berlingo not bad but noticed wen first time vacumining out had wetness under pasanger carpet +rear under floor stores seem to have wetness in them to the extent a litle rust has formed , have ground /treated the rust so not a problem but want to know where the waters coming from, the side door +window seals seem ok although the drivers side sliding door is mis aligned enough to stop it closing properley- catches on driver frount door how can i adjust this haynes book dosent help. cheers lee