It won't be the tube that's blocked, is yours a 3door or a saff? On my 3dr the tube runs from the roof of the car, through the 'A' pillar and then down past the where the door bolts onto the car and then drains straight into the sills where it finds it's way out somewhere near the jacking point underneath the car (I assume a saff would work the same) If waters getting into your footwell then the tube is not blocked, if it was blocked the water wouldn't get into the footwell as it would be stuck in the tube.
I investigated this on mine once when my footwell was filling up but it turned out to be a leak around the fusebox.
I'll try and get a link up to the thread I started when inwas trying to track down the leak on mine as someone posted up a few photos of what causes the water to get into the footwell, it can be caused by the jacking points being crushed up underneath the car preventing the water from draining out of the sills.