They are not allowed. Only eligible sellers can list cots. The used cots you can see are either from non-UK sellers or have been listed in the wrong category to avoid being removed.
New cots: Eligible sellers can list new cots that meet BS EN 716 standards. Sellers must say in the listing that the cot meets these standards. Used cots aren't allowed.
https://www.ebay.co.uk/help/policies/prohibited-restricted-items/product-safety-policy?id=4300&st=3&...
"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)
