Thank you for your question
My name is Clare
I shall do my best to help you but I need some further informtaion first.
Did she hold the account in her sole name and did all the money you have listed go into the account?
When will your Grandson become 18?
Your Grandson will be able to sue his mother for the return of the funds if she does not hand over ALL the monies when he is 18.
He should make sure that he keeps a record of what was in the account - and he can use the Money claim online service when the time comes
Please ask if you need further details