How to buy from HK but pay from UK address

Hi, I'd like to buy my son, who lives in Hong Kong, some tags for Christmas. I don't really want to post them from the UK so went online on the HK Apple store, to deliver from there. All went fine until I put my billing address debit card details in and the website won't let me change the country from HK to the UK. Any ideas on this anyone? Tuia