Great Bank Accounts?

Hello all :-)

I am seriously considering setting up a saving account for my little one, as his mum says she doesn't want me to pay CSA.

I am just wondering what I need to look for, e.g high intrest rates and some more information or tips for choosing the right one. 

I am looking at getting one where the account automatically changes to his name when he is either 18 or 21.

Please help :P 

Thank you!