Thanks, they have replied now and still want it. Tempted to refund the cost of the item minus the postage and relist so they can buy again if that sounds fair? ( seen someone else suggest that)
Checked the address on royal mail checker and they have it on record so no idea why they didn't deliver, just says they tried and couldn't correctly identify the address! Whether this is an issue with the label which I can check or an actual physical issue at the address I dont know. Thanks for the advice 👍