If you pay via PayPal, then until the end of the year you can claim back the cost of up to four returns, for up to £15 of postage each time.
To be able to reclaim, you need to log in to PayPal and activate the 'Return Shipping on Us' offer (it's free and activation's immediate). After that, you can claim for items you buy via PayPal and return by 31 Dec 2016. PayPal says you can reclaim for overseas returns as well.
Source - Moneysavingexpert