[quote=smurfn]I went out to the MINI this morning to find that some caring person

must have taken a liking to my number plates and very thoughtfully thought that I may need to clean underneath them

so they removed the rear plate QUOTE]
unfortunately, if you think something is cool, someone else will. having looked into your gallery, it is a cool plate, so the less desirable element will be drawn to it.
i would resist the temptation to secure it even more firmly with extra screws, etc,as they'll probably end up scratching your car getting it off again (let's hope they don't even try again)
regards,

Ian M