MMA ( Mixed martial arts )

The amateur boxing places here in Birmingham tend to be not for profit setups. Taking a token weekly fee for training.
Try and find a hardcore old school no frills place like this rather than some white collar wannabe warrior stuff or things in commerical gyms.

I seem to recall there being one in Wandsworth when I was looking for the same thing.

There's also Fit Rooms gym on North End Rd that have a full-size ring + bags out the back where they run classes. They were more orientated towards the fitness crowd but there was regular sparring and so forth when I was going there.

I've got clearer ideas if you're looking for a Muay Thai gym...