Looks like I have exactly the same symptoms. Volvo V70 2009 (2008 plate) D2.0
Yesterday I've heard a low rumbling sound when decelerating / engine braking, that lasted just a few seconds. Today I forgot about this and when only half a mile from home the same rattle could be heard. Then when parked heard the noise when switching off. Switched on to check again, and quiet when the pedal pushed down but rattles when released.
What did they say in Volvo garage? I wonder whether I should avoid driving at all cost, or can still commute to work later this week... Just one week after MOT and on the way from the garage after booking trailing arms bushes...
Noise recording:
https://youtu.be/9gUys4O1BwQ