Grandparent gifts

I have opened Building Socity accounts for my grandchildren and plan to deposit money monthly. The account is for under 21s. It is planned that the children will access at some future date although money can be withdrawn from the accounts "as long as it's for the child". The name on the accounts passbooks is "my name, trustee of grandchild name", How should the interest from the account be treated for tax purposes? - as my name is on the passbook should it be treated as my income or can it be treated as the grandchild's income and not be relevant to my tax considerations.

Hi
Please refer to Interest on savings for children