Hi Nick - I have tagged this post into the openHAB 3.2 Release discussion post, and raised the following bug ticket in github:
https://github.com/openhab/openhab-addons/issues/11845
Maybe if you could edit the title of this post to be something like “C-Bus binding throws exception under 3.2.0 release” (now you know what the issue is 
) it may help others in future searches etc.
Now this is where my ability to help runs out, beyond testing any fixes etc, as I’m not a java coder…
However once this is sorted, I can probably help with other general advice on the C-Bus/OpenHAB integration, as you embark on bringing that into your system… Been running it for a while now, and until yesterday, this integration has been rock-solid.
Cheers