*UPDATE* After the stories of children running up huge bills with in-app purchases, I thought I should mention that these instructions work equally well if you are looking to limit the purchases of a child on App Store – set up an account for the iPod or iPad and put money onto their account. They can only spend what is on the account, and so learn to budget their money. Also good for older kids, when relatives don’t know what to get them for Christmas or birthdays. You can buy iTunes vouchers in supermarkets or online.    Most expats come across this problem at some point. You want to…