If you are worried about being hurt or threatened perhpas you shouldn't have got the police involved at all; don't forget he knows where you live and where the bike is - he'll be back to get it again and make another £140 out of you!
I would have made sure he was physically unable to take any other bikes before taking my own bike back for free!
Anyway, each to their own methods - as you say, you have the bike back, and I did note from the size of your bike that you're only a small bloke.
I would imagine there are enough CC users in your area to help out if you have a problem and the police don't show an instant interest!