The buyer would have to pay before you could exchange contact details but funds would not be released to you until the item had been collected and you submitted the collection code.
The courier can supply the collection code at the time of collection. A buyer would probably be reluctant to give you the code in advance.
Buyers who use their own courier are not covered by the Money Back Guarantee and can't return items so the risk is mainly with the buyer.
Make sure you keep all messaging through Ebay and you should be fine.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)