Octavia III - Horn switching

Well this car is baffling me electrically, my old land rovers were far easier to work on!!

I can't work out how the horns are powered in the Octavia, assumed it was a very simple feed and earth in the 2-core loom to the 2 sounder units behind the grille but seems not that simple. I need to intercept the +12v feed that activates when the horn ring is pressed in the car, anyone got any ides where I can pick that up as the sounders seem to have some sort of negative switching going on.

I tried to get at the horn relay in the fusebox under the bonnet but the board it sits in doesn't seem to want lift up and out of the housing and I don't want to break it. I would need to access the wiring below it, any ideas on this score too please??