I think the vestibular syndrome described in the link sounds very similar to what is labarynthitis in humans (I've had this twice, and the first time I could even walk down the stairs safely!!!). Whether or not they're identical, I don't know, but it is certainly the same kind of thing.
Hopefully, as Charley is "only" getting this occassionally and not constantly, then it could be more likely to be something treatable causing it, such as an infection or inflammation. I hope your vet manages to get to the bottom of whatever is causing it!!!
I wouldn't have thought banging into the cupboard would have caused the kind of head trauma that the article was talking about - the examples they gave are being in a car accident or of big fall - so don't start feeling that you (or your OH) have caused this in any way. It may have been a trigger, but I very much doubt this would be a cause.