I used to go to Don Valley Sports Acadamy in Attercliffe. The trainer, Howard, is a little unorthodox but is fantastic. He started to train Clinton Woods before he went on to become Champ.
there is St vincents near west bar police station (but watch out for the prossies!)
there is wellington street , 2 gyms on the corner try them both out
there is herdings where clinton woods trains at
there is woodseats too