I’ve sold a kids bike. the auction has been won. I’ve had no payment but a request for my full address from the winner.

What do I do

Tell them to pay up first! Also suggest a public place to meet up, if you’re unwilling to post.

How are they going to pay, did they say cash?

Did you offer postage or was it collection only? If collection only they will need your address to pick it up, obviously.

Communicate with the buyer.

Meet somewhere away from home if it’s collection.

… then the buyer files a compliant for non-delivery with ebay and gets a full refund because you’ve no proof.

Cash on collection or pay through ebay and post it, one or the other.

You give them your address. Arrange a convenient time for them to come round. Let them inspect the bike. Take the cash and they leave with the bike. As mentioned, don’t take a PayPal payment if they are collecting.

If you are posting then Paypal payment in advance and only ship to the address eBay gives you. Use a trackable form of shipment

If collection then cash only. As above communicate with the buyer to find out their intentions.

Anything else, such as arranging courier collection is usually (but not exclusively) a scam

only ship to the address eBay gives you

and check it has the word “Confirmed” above it as if sending to a non confirmed address you will not have such an easy claim if they say they didn’t get it.

Cash on collection or PayPal and post.
That’s their choice.

Give him your address then take cash on collection, job done. As its christmas there’s a good chance it will be a present so paypal and posting would probably not be an option.