Cheers all.
It's the entire assembly, like this:
http://images3a.snapfish.com/2323232...%3B42346nu0mrj (I know that's not the right item). So the fitting issue is whether the triangular mount on the door, just forward of the window, is the same size.
Studying the photos that I have access to suggests that the passenger side mirror does indeed have a wide angle outer quarter, which the driver's side mirror doesn't. I wouldn't have thought to check for that.