AC Compressor Clutch can't remove

The AC clutch on out MK1 Octavia has started making a horrible squeezing noise for about 10 seconds until the Compressor kicks in. I am trying to remove the clutch so I can swap it for a new one. But I think the pressure plate has broken off the central splined boss so I can't lock it off to remove the central bolt. Anybody know how to lock it to get it off. Video shows both the outer pulley and the clutch spinning independently from the main compressor spindle. https://flic.kr/p/2rZeogN