Try looking for allstars cricket - they run a 6 week programme for this age (and it is separate to joining a club, although run at local clubs by qualified coaches) it’s a great entry level way to play at the ages you mention.
Alternatively, Cricket Dynamics run by Faisal, is a good summer solution, he’s a great coach and has just entered a league for a number of ages.
Both are excellent choices, depending on which time/location suits you best!
“This summer we are offering free cricket matches to our U9, U11 and U13 group when you join the summer coaching, following feedback from our customers we have entered sides in the NEC Colts League.
Details of coaching dates, times and prices can be found at
https://cricketdynamics.co.uk/cd-teams- ... edule.html
Details of matches can be found at
https://cricketdynamics.co.uk/cd-teams-fixtures.html”
Good luck!