Childrens bank accounts

[mjb1]

I'm looking for a bank/building society account for my kids (specifically eldest, who is nearly 8, and the younger ones in a couple of years). Not bothered about savings interest, but I'd like something where they can fill up their piggy banks with loose change and pay it in when it gets to a bankable amount - only talking bags of coppers, 5, 10, 20p etc. We'd ideally like the account to be in the childs name, and it would be great if there was an option to pay in at the Post Office counter. It's mainly to teach them a bit about how money works, and seeing small change build up into a spendable amount, rather than building up a large nest egg of savings.

So far, the only one I've come across that looks anything close is the Santander 123 mini account (in trust for under 10 y/o). But that one doesn't appear to allow banking at the PO counter. Does anyone have any suggestions for kid's accounts that do?