In the end I decided to buy the parts from the local dealer (and charge back) as ope126 suggested, so I could demonstrate to the repairer.
Expensive plastic...
The packing slip is fun reading, and seems to offer some part numbers for the two mystery clips. I didn't have much luck just now on Google though. It's probably superfluous but I'd really like to be able to source replacements independently in case it's ever needed.
