I would say, unless you have travel, go straight for the local one, Kidderminster.
If it's not likely you can get in (most places do take juniors) I'd certainly recommend Wharton Park and/or maybe even Churchill and Blakedown - there must be a bus/train that goes from Kiddy to B'ham.
I haven't played Kidderminster, but I've played the other two a few times. Wharton is out at Bewdley, so I don't know about transport....it's cycle-able!!
Get help from your parents to apply and see what you can get. It shouldn't be expensive either.