In how far is this action "clever"? It isn't even original.
As far as I know, it is a common fear among small companies that some unhappy third parties like unhappy web designers misuse their server credentials to get up to nonsense.
The web designer intended to demolish the reputation of the company. (Who wants to work with a company that doesn't pay the bills?)
However, if the web designer becomes publicly known, it might be a much greater damage to him. Who wants to work with a web designer who has proven to deal with payment issues in a totally unprofessional way, and who has proven to be somewhat proud of misusing trust?
It looks like a one man act from Scotland. If its not him, but someone else later down the line, he'd better get on the stick because right now, the ugly is pointing at him.
Edit: Actually poking around, he seems like a decent fellow, rocking the nomad developer dream on a little coconut island. Doesn't seem like something he should/would have done. That might make this doubly ugly. "Utility Bidder" may have hired someone else for further work who took the whole thing down over a dispute about their little part. That would be most uncool.