Actually, you may need to talk to your committee, unless your strata manager has delegated powers (although most do).
But first, check what is says in your by-laws. I’m guessing that if they say anything, it will be that owners can’t park on common property without written permission.
Also, they should not be parking in visitor parking. Essentially, they are parking thieves – they are taking up common property that they are not permitted to use to increase the size of their storage.
Right now, I would ask your strata manager to send them a letter telling them that they are not allowed to park on common property without written permission and that is unlikely to be given due to their previous lack of cooperation with other residents.
Also, they are not allowed to park in visitor parking EVER as that is in breach of both your by-laws and your development approval.
Finally, your strata manager could outline the processes and potential fines that can be imposed if they continue to obstruct traffic by parking on common property, visitor parking and refusing to move their vehicle.
If they don’t comply, and you have the appropriate wording on your by-laws, have a committee meeting and get the committee to give permission to the people who aren’t obstructing access. That would take care of your concern about upsetting your neighbours.
And while they are at it, the committee should ask the strata manager to issue a Notice To Comply regarding the parking in the visitor parking space.
If they feel they are being treated unfairly, it’s up to them to pursue the Owners Corp – you shouldn’t hamstring yourself by second-guessing what they will or won’t do.
Oh, by the way, fines and costs are now payable to the owners corp for breaches of by-laws so your neighbours will not be out of pocket if you pursue this.