In reply to Stone Muppet:
I may have exagerated, but they do seem to crop up when you are getting a good flow going and are very irritating.
It's the only trail centre I've been to with these, Brechfa, Coed Y Brenin, Cwmcarn or Grisdale don't seem to need them, and don't have problems with scramblers as far as I can tell are they a regular appearance elsewhere?
I'm not saying let them in, just that there must be a better solution. I'm guessing it is a localised problem, but then it not an area that I would associate with what I assume are expensive motorbikes to own as toys.