Luckily I've never had such a problem here and I've only ever had to shoot them on permissions years ago. Very well done on your efforts and I'm sure you'll have sorted them all out very soon.
I'd always favoured my trusted .22 Hobby for Roland duties but you've just proved to yourself the effectiveness of the .177 on rats which a good few others have also pointed out in more recent and enlightened times. Keep up the good work.