To clarify the police won't do anything, it's a civil matter between you and him not criminal.

If indeed he did purchase it recently, if I remember it was a local purchase maybe range and country in Sleaford?. It is unlikely to be an issue on sale as they check all their gear before it goes out the door, including the second hand stuff they sell on. In that case it may be worth checking with them, they won't have sold many of them. Maybe the seller tried to return it after fiddling with it?..if so they might be able to provide extra evidence, for your civil claim, if things dont get sorted to your satisfaction.

It certainly sounds a little suspicious....

Just an idea.

Bongo