Showed clean IMEI before purchase, then that it was blacklisted and reported stolen (which it is not) after purchase. Then they said for another 50 pounds they could still unlock the stolen phone!
Just for fun, I entered the supposed blacklisted IMEI into their icloud unlock service and they were willing to sell it to me again - no hint of a problem. I have reported them to the FBI and will be going to Scotland Yard next.
Steer very very clear.