Have something against free speech? Don't like it - don't read it . . . you have that choice.
noseall has a good point. And once personal insults begin, then you know the 'insulter' has lost the argument. So predictable.
As regards to qualified "engineers", we lived in a house (built 1940's) in which the gas meter was due for replacement. Official gas-men called and did said installation. Smelt of gas once they'd gone, but considered that as they'd just pulled pipes off and re-fitted, it would go after a day or so. It didn't.
Called them back, and this time a supervisor oversaw the operation. Seems they had installed a washer the wrong way round, "All fine now Sir!" Says the supervisor. A week later they were back to do the job again due to a leak from the same joint, in the same meter.
In comparison, and not blowing my own brass orifice (I just like doing things properly), I fitted some gas lighting to our boat (we lived aboard), and got praise for the finish and fittings from a qualified marine surveyor. That was over thirty years ago. Today, I would not be allowed to do such an installation as there would be no paperwork from a qualified gas installer to validate any insurance cover needed for same. Who would I trust to do such work? No-one. But I would have to pay the piper - and then go round checking everything myself.
We live now in a rented house built 1950's, an ex-farm workers 'cottage' in rural Shropshire. There's a solid fuel Rayburn in the kitchen, and an open standard 16" fireplace in the sitting room. We like old stoves, and brought our old faithful - a French De-Ville of 1930's vintage - and popped it into the sitting room with a plate set into the aperture and the gasses going straight up the chimney behind same. I heaved it out twice a year for a DIY chimney sweep (shock horror!) and it had worked and performed perfectly for a couple of years burning fuel more efficiently, and reducing draughts induce by the open hearth. How on Earth did we get away with it - and still alive with no chimney fires?
Then the Landlord phoned one day to see if we still had the open fire, or did we have a certification of installation for the Frenchy, as they were being harassed by their insurers for compliance certificates on all their properties. It might be a problem for them without certification. So out came the Frenchy, and now it resides under the stairs, a hidden ornament, victim of bureaucracy. In place we have more fuel being burnt for a given heat output, and more draughts. I did get a quote from a registered heating engineer for a flue liner (there never has been one), and without stove this would be in the region of £800 - easy roof access and a straight fall, included reg. plate cap and cowl. Then we saw some inset stoves at reasonable prices on the 'net below 5KW output and not needing a liner. I was tempted.
Then I stumbled on this thread, read all twelve pages from start until now, and guess what? I'm spending my money on something else, and all the certified 'Johnnies' can go without my custom. If I can't do it myself - you ain't gonna do it either.