My Skoda with 40,000 miles went for a service.

They rotated the tyres, moved the front to the back and vice versa. Since then the car drones, it reminds me of worn prop shaft groans in old rear wheel drive cars.

I am not sure if it is the tyres or the wheel bearings. The rear (ex front) are 50% worn, the front are 25% worn. The tyres are all identical and have done 20,000 miles.