West End Stage runs week-long courses through the summer holidays, ending at the August bank holiday. They're based at the Barbican with a performance at Her Majesty's Theatre on the final Sunday of each course. Age range from 8 up to either 18 or 21 I think.
Not sure where you're based but High Wycombe Swan theatre run a fantastic summer project 12-25th August. Beauty and the Beast this year, auditions May 19th
be ready for anything and the unexpected never happens
Wycombe Swan Projects are really good but they do have a massive cast. Good value too compared to a lot. Also,if you are more interested in backstage, they need kids there too.
My girls are on an Act2Cam film workshop this week and loving every minute of it. I believe that there is a week-long workshop in York in August, so if you fancy something a bit different but very rewarding, why not google Act2Cam and see whether it suits your plans. Or you can find Steve who runs the courses on this site - just search Act2Cam and you're bound to find him.