I just got an email from gumtree with a code for 20$ off ebay with no minimum spend so I bought 2 round 1966 50c- which were 20$- for absolutely nothing including delivery! I have several gumtree accounts but only got the email to one of them, and years ago I had paid to upgrade a gumtree ad on that account so they might only be sending them to people who have paid for an ad before.
You're the lucky one. I sold a few cars on there the over the past few weeks with upgraded adverts and haven't received anything.
