The Santander 123 mini trust account we have one for our boy 3% up to £2000 as soon as you get over that, you can stick the excess in an mini ISA.
We had one for our daughter as well, that one migrated to a 123 mini when she reached 12, with that came a debit card etc
You can withdraw without penalty's any time.
http://www.santander.co.uk/uk/curren...-mini-accounts
A few on here don't like Santander they will be along shortly.
It's easy and fast to set up.