Can you buy the black bumper inserts for the front and rear separately?

I have a spare front section.

 

I am sure they are dealer order parts if really needed though.

Yes you can order them i replaced front and rear ones, about £40 each from dealer, or of course there is a local breakers.

 

Front......1U0 - 807 - 717C.....08/00 01C (BLACK)

 

Rear........1U6 - 807 - 423B.....08/00 01C (BLACK)

Wasn't it mentioned a few times that the new ones were short on the ends?

Yes you are correct,

 

I found the front one fitted perfectly.

The rear one, when fitted, gave a 2mm gap between insert end and end of the recess on the bumper.

I tried reftting it a few times, cleaned the recess, made sure all the clips were fully seated etc but couldnt close the gap. 

To be honest after a while you just dont notice it any more.

 

Rear

 

Front