Clearing blocked sunroof drains

[RetroPug]

Right.

I removed the wheel arch liner and the wing, I cannot find the drain pipe at all, I think it is inside the box section of the chassis that is behind the top of the wing. Having watched water drain out of the other side, it doesn't come into the wheel arch it comes out of the chassis behind the wheel arch, near the front of the sill.

I've really no idea what to try next...can't see the bloody pipe anywhere.
All helpful suggestions appreciated.