I have a cat fault come up so decided to hit it to here how it sounded? What do you guys think? Right at the end of the video it sound like bits are vibrating...

 Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

It does sound like the core is loose and may well rattle itself to death. If it's still working you may get some more life out of it by slightly denting the canister. I did this on a car a while ago and it carried on fine with no rattles for 3 more years. I put a g-Clamp on it in three places and crushed the out er can.

AJG BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

Bit late on this ..

Have you had a good look underneath at the heat shield? Had a similar issue on mine and like you thought it was the cat. Turned out the heat shield had dropped down onto the cat. Rattled a lot on low revs and also when turning off the engine ..
Couldn't see the heat shield was touching until I got right underneath and looked/ felt along the top of the cat itself.

Cheers

Simon