Those places specialise mainly in dance as they train for theatre dance. I think you need to be able to hold a tune and have a strong enough voice to sing in chorus but you don’t need to have had additional voice training. London Studio Centre is excellent but very expensive. Bird is also good but the intake is huge. Laine has a superb reputation but you can’t get student finance. I don’t know much about the others. There’s Performers College too which has a fantastic ethos and really cares about student wellbeing. The standard is high in all of these places and they are very competitive. Good luck.