What on earth are these two doing? If you and I could not be arsed to spend a few quid on proper locks for our doors and windows, remember to lock our cars and bicycles and so on, would there be some high-level political meeting to discuss it? Or would they leave it to the common sense, enforcement of law and the not so gentle nudges of insurance companies, such as, "Oh, so it was not locked, then we are not interested". Yes, like most large scale crime, whether financial or other fraud or import/export or forged goods, it is international. So, we adapt existing international legal cooperation accordingly. Two politicians worrying about reelection are irrelevant.
There are serious problems for Cameron, such as an election, NHS, actual poverty and he is worrying about firms who can not organise themselves to install proper software or even, if very sensitive, disconnect from the WAN.
As for GCHQ: educate, sort out real, malicious attacks against government systems and point out to industry that it is private, with all the gains and risks that that involves. As usual with crime, the responsible state legal authorities should investigate when they receive complaints. There are, already, international agreements covering this sort of thing, hence Interpol and so on.
Of course, this is just a fig leaf. One has to ask why Cameron thinks this is a good use of his time with an election coming up and serious problems at home. Is this just evidence that he has been called in by the real powers for instruction and briefing?