Makes sense, bought something a couple of weeks back and it calculated p&p based on a US address. I thought it was a glitch and paid, confirming my UK address, but then when browsing on ebay app for iphone load of items in the UK were saying 'seller doesn't ship to your location'.
Checked my delivery addresses and noticed it had defaulted to a friend's in the US I used a few years back. I deleted all old addresses so now just have my primary one.
Good heads up though as it's definitely worth checking, it can affect your searches as well as where your won items may be sent.