I came across this website this aft (whilst looking for child trust fund info) and have opened it solely for my child beefit to go into. The 7.25% interest rate is great even after tax and you can access funds anytime....it would be even better the more kids you have as your CB is obviously higher. My plan is to leave it all in there for a year, then draw out either for Christmas or holiday funds.
www.coventrybuildingsociety.co.uk/savings/Family1st.aspx