Getting interior rattles fixed

[Johnnytheboy]

My Focus's interior trim each side of the back seat is getting very rattly.

I'm reliably informed this is not a warranty thang so it's down to me to sort (and I want to).

Where does one take a car to have this kind of thing sorted?

A good body shop? Or someone more specialist?

I'm in Dorset but don't mind travelling, if anyone has any recommendations.