Good grief
What a shower. Tracing Bob Brown is not likely to be easy, but I maintain that you will never get anything whatever out of Pawl Shanley except possibly the pleasure of passing HMRC or the police enough information to get him in front of a district judge.
It was always clear that BCT was not liquidated properly. Ownership of its assets appears to have been simply assumed by a new company, which was then promptly merged with another firm. As a method of avoiding paying debts to BCT's creditors, this is pretty crass, and up to the standard of imbecility I would expect from Pawl Shanley.
If BCT was not properly liquidated — as appears to be the case — the police should be contacted. The winding-up of BCT seems to have been fraudulent, and I can't believe the police would simply brush off the contents of this message-board (and a fistful of VAT receipts) without at least making a few basic enquiries.
The creditors should present an outline of the matter to the police. There is nothing to be lost, after all.
Good luck.