I havsnt has a proper look at it yet.

If the rear one is down beside the rear lighs in sure i could try and get an airline in it to blow dirt out.

WIll try and run water around it and look for it coming out of the pipes to determine which one if any is blocked.

But if one is blocked how is the water getting down into the foot well? How does it get from the sunroof drain to there?

The boot as far as i can tell is dry.