Where can I find a bicycle "graveyard" in North London?

[morphy_richards]

I'm looking for a couple of smallish wheels and other metal bits and bobs to make a bicycle trailer. Freecycle has so far yielded nothing so I'm wondering if anyone knows of a 'dump' of that kind of thing nearby where I can improve their environment a little bit by taking some bits away ...

 

[Biscuit]

Your local police station might help as to dealers of unclaimed cycles.