The UK also has distance selling rules. These allow for a 14 day cooling off period where the buyer can return the product at their own expense without reason. The problem with any of these kinds of rules is that if the seller is a bad actor, they won't honour it and your only recourse is your payment provider or taking the seller to court. For small monetary amounts it isn't financially worth it, and bad actors will exploit this.

The safest thing is to use platforms (eBay, Abe) to protect you, and if a SELLER suggests going off platform run a mile. There is no legitimate advantage to the seller in doing this, so if they are suggesting you do it, they probably have nefarious reasons . As a BUYER, I have requested an off-platform sale, knowing I have increased my risk (and I've never had a problem).