Go for it !
Update: - I did, and the outcome has been very positive. I was contacted by a very helpful OR project manager, who took the criticisms on board and having seen the pictures agreed that the installation was not acceptable, and that it was indeed OR's responsibility.
We agreed on a site meeting with a Kelly team leader as well. In the event an experienced OR installation specialist also attended. We agreed on a revised installation with proper ducting, and the Kelly guy was actually very constructive and agreeable. On that basis, and despite my previously expressed doubts here about letting them back, I agreed to them doing the rework, with an assurance from the OR PM that I could get back to him if I had any reservations.
Anyway, the KN team leader turned up yesterday with two guys and carried out the rework as agreed. The result is shown in the final two pictures in this link
http://bit.ly/1zrBAlR. It took them most of the day, but this is an altogether more professional looking outcome, and I'm well satisfied with it.
So, my thanks to all of you for your contributions and comments. A good result!
Cheers
Mike