In reply to LaurentZ:
They sound like prats - but in fairness I think everyone needs to have their wits about them. It's a quarry, and a quarry where it's almost inevitable that there's someone climbing above you if you're on the lower tier under the upper tier routes. It's all well and good trying not to pull things off and shouting 'rock!' when you do - but it's not hard to imagine where someone pulls off a hold/block/whatever and takes an unexpected whipper. I don't know about you, but I certainly wouldn't be able to guarantee I'd be shouting anything if I'm suddenly somersaulting backwards through the air. And some of the routes on the upper tier (the two easy ones particularly) seem to be glued together partially with mud and magic. If someone is on one of those routes, I'd just stay well clear. In fact, if someone is climbing above me on the upper tier, I'd probably stay away regardless of the route they're on. It's just common sense.
Not that that excuses what, on the face of it, seems a bizarre approach to loose rock and a blatant disregard for other people. 'Check the guidebook'? What? How's that going to make anyone any more able to dodge falling choss?