|>>|| No. 7409
Enforcement agents operate under time-limited certificates from the courts. They tend to balance the need to not be a pushover with the need to avoid anything that'll jeopardise their ability to renew their certificate, such as a complaint to the police. If they won't believe you when you say you're not the one they're after, tell them that you're going to close the door on them and you'll call the police if they come back or don't leave.
Incidentally, one of the more pleasing small victories over bailiffs I heard was from someone with a stable door. As soon as they have their foot over the threshold, they secure a continuing right of entry, which is why they'll try it as soon as you open the door. It turns out it's pretty difficult to do that if only the top half of the door is open.