Always best to read the return goods policy on a website before you buy.
These scam China websites or Social Media ads you buy from will NOT have a return address on their website and rarely a phone number, so thats the first sign its somewhere to avoid.
They use issuing depots in your country to send the item but the 'return' depot is normally in China and as UK was not on their website as a return address then you have to return it where they tell you to do so.
In the event of a dispute you need to bear in mind possible return trackable costs before you buy from that seller / item / country because....
Paypal state this >> PayPal is not obliged to reimburse you for any costs that you incur to comply with any of PayPal’s requests for cooperation for the purpose of resolving the problem (including, without limitation, costs that you incur to return a SNAD item to the Payment Recipient or another party as PayPal requests), although sometimes it may reimburse these costs.
Although they will compensate you for some of the cost if you have activated this at some point before you made that transaction.