Jon, I'm sorry, but your utter ignorance of this subject is only matched by your lack of desire to correct it.
Of course this lady's opinion isn't guaranteed to be correct. She has only investigated in detail every single UK death from CO and gas explosion for the last 20 years. Every single one - including attending inquests, counselling the bereaved and recording the statistics. I am sure that your opinion is supported by equally thorough research? No? Well there's a surprise!
And you continue to make the most naive assumption of all. If the untrained DIY enthusiast is denied access to the proper materials, then off course he will immediately see the error if his ways, and retain the services of a qualified engineer. There is absolutely no chance that he will try to use garden hose in place of a cooker hose, or source 2nd hand parts via Ebay, to the still greater risk of his children, tenants and neighbours.
Please bear in mind that I run a trade only business, and it would be substantially to my business advantage if this sort of policy would help, but not only does it divert resources from more useful campaigns, but on its own, it would probably lead to more, not less deaths.
So can we please stop repeating this complete ********, and actually research the effing situation?
<sorry mods - just realised my last sentence set of the profanity filter>