In reply to noviceclimberkate:
Kate,
I believe Vauxwall in London has no lower age limit (assuming an accompanying and competent adult I believe). I remember asking them as I have a young nephew who I would like to take.
Louis Parkinson teaches out of there, I can recommend him personally for adult lessons, and have seen him previously with younger children also. He recently started a company: Catalyst Climbing. They do climbing lessons.
George