I, (like so many others), have been told you can install but not commission a gas boiler and then get GSR to commission it.
And he checks everything and it's correct and safe, fair enough, in a perfect world; but as the whole world knows, this is not a perfect world.
As someone posted this above I would agree with them, just as I agree that there could be a "tick box" (Quote, Steve the plumber), to say it had been done by someone unregistered and it needed following up.
But it appears to me there is a gap in the middle.
It's a bit like a two trains leaving two separate stations traveling at different speeds, but they have to meet at another station inbetween to exchange passengers, but something is wrong with one of the trains and it falls short.
So who helps the passengers?
Considering both measures allow unscrupulous people in to make a fast buck with no regard to safety there is only one course of action IMHO.
I did have the view the unregistered could just do the water pipes; but how does the GSR know they have all been done properly; has the flue been done properly; has the boiler been secured to the wall properly, so many possibilities that the GSR will be blamed for.
Unless it was done by an apprentice while being watched by GSR, the work should only be done by a GSR; gas line, water pipes, heating pipes, cylinder, expansion vessel, only by GSR and they are confirmed as GSR at every job.
Time and money, yes, but what other options are there.
FYI, I know an unqualified someone who has installed unvented cylinders, he says "Nah it's fine, it's just a cylinder".
Give 'em an inch and they take a mile.