I prob would wait till Paul gets back to you, and if the boyfriend doesn't get back to you, I'd just keep going there an bugging them until he does, surly he will be able to get a hold of him.
I wouldn't be going into anyone's garage to take back, your or anyone else's parts.
How would u feel if someone went into your garage, going though your sht and everyone else's.
In saying that I'm not defending Paul, I've had my own issues with him. Which are similar to yours, and it did my head in.
But I just don't think going into the garage is the right thing.
You would need some sort of police warrant to go there smash down the door and get your gear back, the police would have to do it all, and you would need to supply proof that, you haven't paid for Paul's services, and that you own everything you plan to take.
Hassle the boyfriend, get into contact with Paul. When his back, hassle the fark out of him. Once you get your sht back, never use him again.
Simple