Vibration problem on my S40
 

So I have a vibration problem with my S40. It's a constant womping noise that is apparent at speeds above 30mph, which gets louder the faster the car goes. It's there regardless of the direction of the car, and when the car is in neutral, so it's not transmission or cv joint related.

I have new tyres and the wheels have been balanced, I have fitted new hubs/bearings on the rear on both sides and this hasn't fixed the problem.

I think it could be the front wheel bearings, but does anyone know if there's anything else I can try before I get them done?

How recently were they balanced? After I had new tyres fitted I discovered a less severe vibration but they'd fitted the wheel balancing weights to a part of the rim that scuffed the caliper every time (I only went to a big name national garage as they were the cheapest for the tyres I wanted but this is the quality of work you get).