Well, someone has used your account and registered it in China, that is the place of registration showing now.
It's not a simple matter of just changing address details, for this you need eBay Cutomer Services, who have access to your account and can explain how to re register your account correctly, if you are now residing in the UK.
To Contact Customer Services, I find the quickest way to contact them, either for a Live Chat, or you can select to speak and request a Call Back, to click on this link:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
On weekdays lines open between 8 a.m. and 10 p.m.
On weekends they open between 9 a.m. and 6 p.m.