This part was found after we’d put everything back together, its not obvious where it fits and we couldn’t see any broken parts inside.
In the best tradition of car repair we noted its part number and it now sits in my office draw!
The car has been driven extensively over the following two weeks and there are no rattles present, with all componemnts working normally.
EDIT Steve searched the part number –
The part we found afterwards was in fact part of the centre console trim on the left hand side, apparently to stop rattles, it was a U shaped piece originally!
Like I said no rattles are present as it is…