Engine 850: B5254S/2.4/20v: Failing Cat - would it cause these issues

[Spooky]

Hi all, it being a Bank holiday weekend my normally perfect 850 has decided to grab my attention by playing silly buggers!! Earlier this week I noticed a rattle coming from the exhaust when I started her up but it seemed not to be so noticeable after being warmed up. All was fine running wise until coming home friday, she seemed not as sharp as normal. Went to autojumble down the road(cancelled, ever get those days when everything conspires!) and coming home she suddenly lacked power but still ran. When I was about to turn left across the road into my road she gave up and died. Coasted into my road and tried to start, which after a lot of effort she did but stalled when I applied any throttle. Again got her going and crawled along not using any throttle, its an auto so just poss to move. Had a look around and the cat converter is very rattly, plus at this point the lambda light came on. Sorry for rambling but could these issues purely be from a failing cat? I have reset the lambda light and it seems to be running fine, blipping throttle does not stall it. It did sound very rough, as though the manifold or exhaust was blowing; any suggestions as I now have to try and get a replacement cat, the earliest quote from kwikfix is wednesday, cheers, Dave