Is blackmail and extortion not a criminal act? By refusing to hand over the information and equipment (which is unrelated to the disputed invoice) he is causing enormous damage to the company. He has access to all our emails and there is also a privacy issue.
Our contract clearly states that all IP etc vests with the company. The fact that we cannot access our website hosting etc is materially affecting our business - how would we file the Court claim and what would it cost. Perhaps most importantly - how long would it take?