I did a couple of posts about the former Preston Library building here and here. As I explained, there are a number of problems with the hope of the Friends of Preston Library to simply take control of the building. In my view, indeed, they are insurmountable.
One that I didn't mention is the importance of guaranteeing performance. The days when Brent just gave people money and let them get on with it ending a long time ago, which given the potential for abuse is probably no bad thing. The many organisations that get grants from Brent: Brent CAB, the Tricycle Theatre, all sorts of ward working schemes and many others are required to report on progress towards whatever the objectives of the grant are.
Essentially, you have to list your objectives, have some sort of reporting mechanism on whether you are achieving them, and a correction mechanism if you do not.
In the case of a building, I would expect this to be a clawback mechanism, where if the building ceases to be used for the stated purpose it returns to the ownership and control of the Council. This is a long established principle of such arrangements, for example it applied to the old Carlyon Plant, the Bridge Park Sports Centre, Brent Museum and others. I have remarked before that, despite their increasing ubiquity, there appears to be no agreed criteria for measuring the success of community managed libraries. The closest I can find is this.
Ignoring such issues does not make them go away.