[Ian21401]

I guess that the drain is supposed to exit somewhere in the area of the rear wheel, but there may be a leaking joint hidden behind the head lining. Someone who has had a head lining out may be able to comment. I had a regularly blocking drains problem on my daughter’s V50. (Main cause being an angled joint at the bottom of the A post just before the drain passed through the bulkhead.). I used a long piece of curtain wire ( the plastic coated wound wire type commonly used to hang net curtains) carefully pushed into the drain from the sun roof, twirling it as it is fed in. It’s a fiddly job but did the job.
I’ve seen suggestions that compressed air may help, but I don’t know the success rate.
I had a leaking drain problem wetting the headlining on a Ford Orion. Both sides above the rear passenger doors. I carefully freed the edges of the headlining above the door aperture and found the plastic drain hoses had a metal jointing tube. The metal had corroded. Fancy joining plastic hose with a cheap metal tube.