I still love my 125d.
Diesel noises are at a minimum. You get some at startup, but as soon as you get going, there's no real tractor sound or anything similar. Even when pushing it, it still sounds reasonable for a diesel.
This is me, going on the Nürburgring and you can hear the cabin sound pretty good.
There is no radio on and as soon as there are other (petrol) cars I can barely here my engine.