We have fixed the rattling exhaust.
The trumpet end was a nice fit in the exhaust, so it wasn't that.
What it actually was, was the mesh tube was slidding up and down inside the exhaust and rattling around. It was sliding so much that it was marking the inside of the tail pipe.
To solve it, we put a jubbilee clip on the mesh (not too tight at first), re fitted the tail pipe so that the jubbilee clip slid down the mesh until the tail pipe was in it's final position. The pipe was then removed and the jubbilee tightened.
Problem Solved
It is ammazing how much difference it has made to the exhaust note. It's awesome!!!!
Thanks again for your suggestions.