disable branch modification

Hi all, I've got a remote git repository that I want multiple users to be able to push to. This is all set up fine and working beautifully. The only thing is, I want to be able to lock down the branches on this remote repo, once set up users should not be able to:

1. Create new branches on it
2. Delete existing branches from it
3. push non-fast-forward commits to it.

I think I'll need to write a pre-receive hook for this, but before I embark on this, any helpful pointers would be appreciated.

Thanks, Ishaaq