I've thought about this terrible man today, MayHug. He really seems to think that he can take advantage of you. If he gets into the garage, it's possible that other things of your DH's will disappear, too.
I agree with the PP who say to call him and tell him that he'll have to rent the scaffolding. Otherwise, he may show up with someone to "help" you move things around in the garage. Then he may act hostile when you don't want him in there. People like this often try to guilt and bully others into complying with their wishes.
You can also tell him that nothing is leaving the premises until your family has chosen things that they might want. Tell him that you are all so upset about the sudden passing that the apportioning of possessions will not be happening anytime soon.
I know that I sound like quite the alarmist here - it's because I've read a lot in the archives of ehell. There are a number of stories on the main blog of people who move in like vultures after a death, and try to take anything not nailed down. At best, this guy is clueless and entitled.
You have been through such a difficult time, Mayhug. My thoughts and prayers will be with you and your family.