Thanks for all comments, guys and gals.
This work of art has now been removed by its author.
A classic case of now you see it . . . now you don't. 
Stuntman
i like it, especially as it builds up to a very definitive punchline
mind you, you might need to emphasise it a bit more, he gets in passenger side of car, or starts to inflate armbands
and then gets asked a question
Very good, professionally written sketch. Nice and quick and punchy.
Great build-up. Not 100% sure about the punch-line. It works but the great build makes you want an even stronger one. I'm hopeless at punch-lines but something quicker maybe like "Er, you know when I said I could swim..?"
I could see this working well on a T.V. sketch show.
It's really funny, can you visualise the Directors face...
This one is perfect!
I liked the gag and it didn't go the way of the Fast Show stunt man which is good. But the director's opening dialogue is pure exposition without anything being added in the form of humour:
----------------
DIRECTOR (SHOUTS):
Right, as you all know, we’re six months behind schedule, two million quid over budget and the backers are screaming like stuck pigs. If we don’t get this in the can before the light goes this afternoon, we’ll all be on the dole tomorrow morning! We’ve got about ten minutes.
---------------
The crew definitely know that they are 6 months behind etc. The Director is only telling the audience but your audience is familiar with the pressure involved in getting films shot quickly. All the "Ready?" "Ready" interchange could be removed too, imo.
If you started the whole sketch from the Director leaning into the car window and modifying his opening line you can condense the sketch to its ESSENTIAL gag, all the fluff and bump taken away:
---------------
DIRECTOR (TO DRIVER):
Okay, we've got one shot at this. Along the quay at full speed, hard right into the blind alley, hand-brake turn at the end just as seems you’re about to hit the wall, full speed back to the quay, hard right and foot down towards the crane, swerve to miss the oncoming JCB, straight though the stack of cardboard boxes and off the quay into the drink. Let it sink to the bottom, struggle for as long as you can with the seat-belt then come out through the window and up to the surface. Any questions?
---------------
But as I said I did enjoy this and it is excellent formatting, sir / madam.
The punch line seems a bit removed from the set up....does a stunt driver have an application form?
In my mind it went....
DRIVER: (puts on a swimmers nose clip)
Which was the peddle to make it go faster again? (said in a nasal voice....of someone terrified and wearing a nose clip)
But i just think nose clips are funny
The trouble with this, I think, is that given the final spiel from the Director, one anticipates a certain punchline. And you deliver it.
maybe it could be a series of sketches with the stuntman saying something different each time...like...
do you know how to get Classic FM on this?
can i just pop to the toilet?
which one of these is the indicator?
you're terribly good looking.
etc
Thanks for your comments guys and gals. They're much appreciated.