Re: Theft of data
Different orgs for different purposes. Theft and hacking would be the home office, fraud the SFO. This is about the legal (well, lawful I guess) obligations to secure personal data.
I'll analogise with cars (even though I hate them) because they seem to resonate with people. If you leave your car with valet parking and they leave the keys in it and it gets nicked by a third party, you'd likely pursue a civil claim against the parking operators. A crime was also committed, but if the plod catches the thief and the parking operator keeps leaving the keys in vehicles, not much gets better. Ideally you go after both with the appropriate organisations — no idea what chasing the perps would fall under in this case but probably Computer Misuse Act or some later addition if domestic.
That's the idea behind the ICO and such bodies and the associated laws and regs anyway. They're pretty crap when they meet reality. In the realm of the Internet at least you need PCI/DSS accreditation if you're going to be processing card data in any way, and you're at risk of having your accreditation revoked for an audit failure unless you're big enough to buy them off. That's a sidenote, but I can tell you that PCI/DSS teaches you to protect and freak out about 16-digit numbers.
There's a similar culture in healthcare about NHS numbers even though they can't directly identify much about someone (YMMV on how strongly people feel about this — I've worked for third party providers that guard them like gold, seen data sharing agreements with the NHS advising similarly, but OTOH have a local phlebotomy service, entirely understand the NHS, that wants you to email your NHS number plus other details to them to book a blood test; the alternative being a phone number that they only answer for a five-minute interval each time the moon is in waxing gibbous).