You do not send the item out until eBay have sent you a message that the buyer has paid. Send it fully tracked only to the name and address eBay provide on the delivery details for the order and to no other.
If an offer has been accepted, they should be instructed that they have to make an immediate payment, unless you have specifically removed this new ' feature / option' from your Site Preferences.
Listen to no excuses from them, eBay allow a buyer 4 business working days to pay you, they also send the buyer a reminder after 48 hours to pay.
Then, if there is still no payment when this time lapses, proceed this way.
On My eBay Selling go right of the item sold and from More Actions select Cancel this Order selecting the reason .... Buyer Has Not Paid.
If you are on the Seller Hub, go to your Payments tab near the top of your eBay homepage, from there select All transactions. Click on the highlighted item number go far right and from the big blue button down menu there, select Cancel this Order as above.
This gives the buyer an unpaid item strike, they are only allowed one.
If they keep gaining these strikes, eBay will remove them permanently, from their site.
Cases are very effective.
Block all non payers and troublesome buyers from returning to your sales here:
https://www.ebay.co.uk/bmgt/buyerrequirements
