The visual and performing arts are one of nine sectors within the creative industries. The below links are great places to look for more general careers info for all the creative industries and not just theatre.
Creative & Cultural Skills gives young people opportunities to work and learn in the creative industries. They are an independent charity that provides careers advice and guidance, promotes apprenticeships, and delivers activities for young people through their National Skills Academy network of industry and education supporters.
Upstart Projects creates opportunities for young people to develop as the arts professionals of the future. They support young people to lead and manage projects, act as ambassadors, find their voice in the arts and train other people. In short, they offer real experiences which build skills and can lead into arts and media careers.