I can't see anything in your post which necessarily indicates that there's been any breach of the Data Protection Act.
Given a few starter points, it's not difficult to track down someone's previous address from, for example, old electoral records. (The electoral roll is a public document. 10 years ago, the national electoral roll would have been available on CD and, at that time, the CD would have contained the full, rather than the 'edited' roll as it does now. Access to the old CDs is still possible in many public libraries. I frequently make use of these CDs myself).
Once your neighbour had your old address, there would be nothing to stop him contacting your former neighbours (assuming that they'd not moved away) and asking about you.
Similarly, courts are public places and basis court records are public documents. (You can't normally access the evidence which was placed before a court but you can read basic details of the case and the court's rulings). If your dispute was heard in court, it would not be difficult to find out some basic details.
Chris