I had a similar leak driverside on a 96 celebration. It has a rubber rain channel which was basically too small and did not catch the rain coming from the windscreen scuttle.It then came down the A pillar inside the Sill carpet onto the floor.
With the door open run some water off the roof so it drains down the windscreen channel and see if it meets up with the rubber channel.If it dosent you will see it running down and inside to the sill and carpet.
With the door open run some water off the roof so it drains down the windscreen channel and see if it meets up with the rubber channel.If it dosent you will see it running down and inside to the sill and carpet.