Where was the horn located and what did you replace it with? I have ran into an issue with my horn having stopped working, clock spring and fuse are all okay. Horn has died on its own, I plan to replace myself but struggling to find any info online.
It's located within the bumper space, low down and offset towards the driver's side. There's no need to remove the bumper, certainly not in the case of a Leon Mk 4 / 4.5 - other cars might vary!
Remove the engine tray and behind a flap/panel to the forward right side (I really wish I'd taken photos!) you'll find the horn. It's a bit tight for space but the single tone was removed and a 'previously enjoyed' twin horn from an Audi TT was installed in its place. There was some minor wiring involved, not a big deal.
I hasten to add that my local and very helpful VAG indie did this for me in less than 30 minutes - the car was in the air on a ramp so that obviously made the job easier and quicker being able to have proper access and not crawling about on the floor with the front up in the air on ramps/jack.