Thanks Bill, I'd like to think that the case and many manufacturers may do this, VW though seem to have about half a dozen or more seemingly different designs for a VW Golf mk6 2.0TDI.I just stuck aircon compressor clutch into Google, and came back with results. Not specific to Golf of course, but it seems Autodoc list for many models.
I would expect the compressor, and clutch to be generic, so not that many options. Vehicle manufacturers are likely to use an existing unit, rather than have a bespoke unit designed, so hopefully just a case of choosing the right one.
The official model of my car is a
Volkswagen Golf Cabriolet 2.0TDI Bluemotion Technology.
and is the late 2015 euro 6 version, so its got very specific parts to safe energy and fuel related to the Bluemotion system.
Things like a coolant pump that can be switched on and off if its not needed, and alternator that can push high currents and voltages when not on the power but switch off completely when the engine is under load. given this I suspect there is some gadgetry in the aircon compressor too.
VW being VW I am sure it is a common part used in several different models. maybe with the pulley being different I'm hoping that if that difference applies to this pump that means I can get the clutch separately.