I think you?ve made a profoundly positive decision to learn to sign. Since your little one is hard of hearing/deaf, attending classes or studying books is not the approach I would recommend.
I?ve never taken a sign language class in my life. Over the years I?ve come to realise that no one can 'teach' ASL (or BSL in your case). All a teacher can do is present concepts and model success. The only way language is truly transmitted between people is through 'LEARNING'. In other words, don?t go to a teacher ? go to Deaf people, and try to understand what they?re saying.
At first it will be terribly frustrating, and you?ll feel like you don?t belong. But don?t give up! Never, ever give up! Keep with it, and soon you will begin to understand some of the concepts being discussed. At some point you will want to join in the conversation, and feel very frustrated that you don?t know the grammar, even if you do know the signs. Keep struggling. Try your best to THINK in BSL, rather than relying on English.
After a period of time you will find yourself participating in discourse, and understanding everything people are saying. And don?t be frightened at being corrected by Deaf people. Deaf people are blunt and honest ? just like the Tutors at Cambridge, they expect proper usage of the language. If a Deaf person is willing to take the time to correct your usage, you?ve been accepted!
Most Hearing people who take the language are simply acknowledged and ignored by most Deaf people. But because you?re unique, because you?re ?one of us? they will embrace your efforts and encourage your language improvement.
3 Cheers for Deaf people who learn their ?native? language!!!