Unless information is secured by role and by purpose, which I gather it isn't, then security will be impossible. CRB checking is irrelevant - its not done every year, its not spot-checked and anyway it doesn't take account of marital status.

All it will take an authorised person with personal problems. Wasn't there a police officer got done recently for trawling some database for his ex's whereabouts not so long ago? Aren't there cases of teachers in court for alleged child abuse? And thats only the ones who got accused / caught.

So with 300,000+ users its guaranteed that somewhere someone will be an as-yet undetected offender, or desperate for money to pay off debts, or desperate to find their old school buddy's kids for him. And every single day someone will do a screen-print or other hardcopy and leave it lying around somewhere. It'll go home in a briefcase, be left on a desk, be dropped while fumbling for keys, be used to scribble on the back of.