Why do you need to "track him down"?
If there is a case against him the police will do everything themselves. Serial scammer Dean Nolan does not need to be tracked down for any reason at all except if a criminal case for fraud and theft fails, in that case a civil case against him would be the route.
Investors should stop believing him about getting their funds back and should get together to report him to the UK Police because he is a compulsive liar.
The problem is you can't prosecute someone for criminal actions, only the state can. And as Dean has calculated, the chance of prosecution is going to be pretty low. While reporting the crime is a good first step, in the past with similar situations absolutely nothing has come of it.
On the other hand, a civil case is something you can actually do yourself and pretty much guaranteed to win. The burden of proof is much lower, and there's no way Dean's going to waste his scammed funds on a lawyer, he'll just pay out that/those particular people and save himself the trouble. So the only real issue is just to start a civil case, you need to serve him. I'm not sure about UK law, but generally you need to physically serve the documents to the person. Hence "tracking down" the person to serve them.
(So while it's a great idea, also be very very careful about pre-paying someone online to do it. You don't want to get scammed again...)