While I would agree with being extra safe, you would not believe the number of genuinely enthusiastic staff we have that just get fed up of waiting for a CRB check to come through.
Quite frankly, I don't blame them for leaving after six months of waiting. When you're working full time who wants to spend their valuable weekends off sitting around unable to get involved just because some pen-pusher can't be motivated enough to push his pen a little quicker?