At the moment there appears to be approx 100 (or at least that I can see) but there were none until a couple of days ago when I first saw one and squished it.
I'll probably have to bear with it until Tuesday anyway (darn bank holidays

) and then get in touch with the council and see if they can do anything about them, so I'm really thinking about something that will just control them a bit till I can get someone in to sort them out.