There's the possibility of three things going on here.
1. There was a recall on these cars which involved the removal from inside the N/S inner wing of a 'duckbill' valve which I think was the outlet for the scuttle drain and which blocked.
2. The pipe from the drain runs under the pollen filter case and kinks at a bad spot. Pollen filter has one 10mm bolt then swings up out of the way giving access. Yellow arrow is the bolt.
This is where mine kinked.
And the repair I did. Split an old rad hose and supported the bend so it wouldn't kink again.
3. While you're in there pull the hose away from it's hole in the inner wing. Shove a couple of feet of 1/4" pipe up till it stops. Cover the grille with a towel then blow compressed air up the thin pipe. Somewhere up there there is a restriction which can probably be accessed by removing all the windscreen surround plastic...........But my way works a treat. Don't forget the towel !!!.
Just had a look and all's well, looks like mods have been done, probably recall work by the looks of it, sorry should have took photies, will do next time the bonnets open, and that won't be too long going by my experiences so far,