Well i have finally had my air con compressor fixed. VW agreed to give me 30% or so and the dealer then beat the next nearest quote by £50 or so to bring the final sum down to less than half the original quote of £1300.
I'm still chasing VW as, in my eyes, this is definitely a design fault with the original compressor and really no one should pay for this work to be done.
However, since the compressor failed the ABS pump died (another hugely common fault and £1500 bill) literally the week after the air con repair. I was going to drive the stupid car into the sea but VW paid the full cost of the ABS repair. Not a full win but near enough so I think I'll let it go.