I have an Octavia III and have put sound deadening (both Dynamat and closed cell foam) on the floor from front to back, doors and the wheel wells. While it made a difference to general noise it didn't make much difference to the tyre noise.
I'm more pretty sure that it is the suspension transferring the noise. I think this is because it is connected directly to the body without any insulation. Older cars with chassis had rubber mounts between the suspension and the chassis, modern cars like skodas don't have that same chassis so the suspension noises are just transferred straight into the body.
I did my sound deadening myself so I didn't lose much. Knowing what I know now I wouldn't p pay someone to do it because it doesn't solve the main problem.