Hi - just throwing it in the yoga mix, but there is a wonderful Bikram Yoga Studio in Balham - on Hildreth Street - called Hot Yoga South. They do a deal for beginners £45 for 30 days - so you can try it and decide if it's for you (although be prepared to hate your first class as the heat can be a bit much first time).
I started two years ago with no previous yoga experience and just fell in love with it - now I am hooked. You don't have to be flexible or fit to give it a try. The teachers are all lovely and I like the family feel to the studio - so after a while you start to know the staff and other yogis too.
http://hotyogasouth.com/

I can recommend Battersea Yoga - they have a beautiful studio by Battersea Park and lots of wonderful classes -
http://batterseayoga.com/

I'm only a beginner but have enjoyed the sessions at Union Station Yoga on Lavender Hill.

If you can venture as far as Tooting, there's a simply wonderful Iyengar yoga studio there. I live in Balham and it's only a short hop in the car. It's a studio with extremely well qualified teachers, very good value classes all week and weekend and a truly yogic spirit.
Check out
http://www.iyyoga.com

Hi,
Could anyone please recommend a yoga class for beginner in the Balham/Wandsworth are.

Many thanks in anticipation of your reply