Seek Advice: Places to play drop-in football in London, UK

I would be visiting London (actually Charlton) in a month or so, and would like to play football, basketball and/or table-tennis for at least 3 hours on any day of the week.

Anyhow, where can I go to play such sports? In Canada, where I am now, we can go to the local university to play such sports on a drop-in basis for a small fee. Which universities (close to to Charlton) offers access to their facilities on a drop-in basis?

Thanks in advance