The bike pretty new (12 months), so crud shouldn't be an issue. That said, I have given it a good dose of WD40, see what the morning brings.
Unfortunately, the collar is shouldered into the mounting boss, so I can't make a puller of the type you suggest. I've even tried getting warm (Not hot cos' it's Painted) & pulling it out with alligator pliers, but no luck. It really is an awful bit of design work.
Thanks for the ideas though.