Once that SD label is purchased, it automatically says the item is dispatched, if you then post in 8 days, you will receive a late delivery defect on your account.
Explain this to your buyer, and that the best way forward would be to cancel the listing, and then it will be relisted for the buyer when they come back from holiday to buy again.
Cancel the order citing Buyer Requests to Cancel, this does not affect your seller performance and fully refunds the buyer.
For the Simple Delivery postage label,
- If you selected 'Buyer pays’ when you created the listing, your buyer will automatically be refunded for any Simple Delivery label that isn’t used after 30 days
- If you selected ‘Seller pays’ and offered free postage on your listing, you'll need to fill out the Request a refund for Simple Delivery form for the label that wasn’t used. Make sure to send your request within 14 days of your item selling.
@senga-doozer