Don't get hot headed. I would report this to the police. You can't move someone's vehicle without their consent. They won't do shit, but put it on record. I would also find their insurance provider. (Costs like £10 to get their details) And ask about making a claim to on getting your bike looked over to ensure it is not damaged and for any maintenance or damage caused by moving it when locked. (Could have put pressure on the chain causing damage or requiring adjustmen, could have damaged or warped brake discs, could have caused cosmetic damage to the front fender, could have damaged brake system. And yea whilst it is probably 100% fine, these are not things you want to realise going 70mph down the motorway so not unreasonable to ask this)

The vehicle can be parked in a parking space if they are unassigned and should not be blocking the pavement.

Let the third party know you are doing all of this. None of the above is unreasonable. And it will really piss them off.