Probably would have been less spoof like and blended in better if the sticker maker hadn't used "dodgy stuff". The real poster on the subway in Japan may have been an influence.
These semi passive aggressive notices in public places, have to turn the "You wouldn't do this at home" message on its head, which is sometimes quite hard. Our office manager sent out an email about keeping the kitchen tidy last week & said "leave the kitchen as you like to find it. On second thoughts, if you're a slob at home, scrub that and just keep it tidy".
Perhaps more Tube notices should be written in this tone.