Also if those boats are sufficiently ferrous to be attracted by a big magnet I wouldn't have thought they'd be buoyant enough to make the Channel crossing. Someone should tell the people-smugglers about vessels made from light, durable fibreglass or inflatable dinghies.
as someone who lives 5 minutes from that cliff, I can tell you that some of those boats appear to be coming from the middle of the Atlantic, I guess ultimately Brazil, while others are coming from Norway. The situation really is worse than we though.