Payment Problem

Use the address where you are now living. Do you have a mailing address in the UK?

Log into your account in the App Store/iTunes and you should be able to change/verify it there. Or you can click the blue Edit payment methods in the article below. When signed in and the page loads, you will be on the credit card page. After updating that, click the Go Back button at the lower left and you will be on the address page.

Apple ID payment information - change.  

See If your payment method is declined in the App Store or iTunes Store https://support.apple.com/en-us/HT203005

You can get Apple telephone support  for help in solving your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362  Be patient sometimes Apple support is closed to immediate phone support.

And here is how to contact iTunes worldwide support via text or chat using this link https://support.apple.com/choose-country-region/itunes After choosing your country, see the heading Tell us how we can help.

You need a valid credit card issued by a bank in the country the store is in and you need a billing address in that country.