1). Is there anything worth recovering in the cat from a 300 TDi?  and if
not, how do they justify the £250 extra cost for a "cat" pipe compared to a
"non-cat" pipe?

2). Out of academic interest, is there a way of getting a "cat" front pipe
off the 300 TDi (with front anti-roll bar) without cutting the pipe or
removing half the front suspension?

the "non-cat" pipe will *just* go on in one piece, luckily...  

doesn't appear to make any difference to the smnoke.  If anything, the smoke
once running and warm looks to be less, not more.