The random numbers you may be seeing are eBay's sort of ' tracking' for the buyer, you do not need to write this if buying your own postage. If using Simple Delivery eBay print out the label / QR code for you to use.
Does it matter that the phone number is not a UK one ?
Once the buyer pays you will be notified by eBay, you post only to the name and address eBay provide on the delivery details and if you select Simple Delivery, should the item not arrive or arrive damaged, then eBay handle and pay the refund not you.... there are some exclusions for eligibility to SD, check your item is not amongst them.
This link explains the Simple Delivery process:
https://www.ebay.co.uk/sellercentre/postage/simple-delivery?mkevt=1&mkpid=2&emsid=0&mkcid=8&bu=43952...
@2711danielleh