Not quite following your point. We already have non compulsory licensing, the RYA day/coastal/yachtmaster programme, and it includes the col regs. Is there any middle ground between that and legislation?
I think there is. For a start review / expand the non compulsory licensing to have a separate module for the col regs so that this is more accesible and cheaper than having to cover it within the current programme of day/coastal etc. Once this is set up, insurance companies could then make it a minimum requisite for cover. For a non legislative initiative to work, it needs to be accessible, cheap, well promoted and useful i.e. required for insurance. Other companies / organisations could then also require it as a minimum.
I realise this could be a trojan horse or thin end of the wedge for opening the door to legislation, but it may also delay such formal licensing as has been the case when other industries have "self regulated", at least enough to appease whitehall.