Inside wheel arch to the front of the wheel I think
Driver side underneath the battery.
on my eco the horn is on the core support.
Why not lie on your back and get someone to sound the horns. Two horns surely less ECO than one, any way
The horn behind the grill works but not loud enough to my liking with just one horn. I'll get to it soon. Can't believe VW have that horn so well hidden. Why?