The bike rack is on the roof in a car park, its accessible by general public but is not on the street. I live in Manchester, England, its got quite a bad crime rate. The thing is though that there are quite a few locks on these bike racks and so many bikes get locked to them.

I am just waiting for another lock to come in the post. The one you recommended in your first post. (thanks!) I have currently got 2 locks on it but one is crap.