I had the same problem a month or so back... I went out and asked them nicely to go and play on their own road and got a load of slather back. So I threatened to kick the biggest ones arse...
I felt like such a cnut, but theyve not been back since
I've had a few problems with attempted break ins on my garage (Few MTB's and the Cossie in there), so I was getting windy about them hanging around
Neil.