the other answer is cr*p!!!!!!
the mk1 renault laguna has (in renos words) a water ingress problem. this is caused by heat distorting the rear door seals and allowing water to pass through in the little channel at the bottom of the door on the kick plate the only way to stop this is
1) replace the seals with the new modified seals from reanult which cost about £60 for both
2)use silicone to fill the little channel
ps anymore questions i will be happy to help
a disgrunteled renault employee(mechanic), January 2006