i think the problem is with the definition of 'competence'...
it really should be 'gas safe registered' and to get registered I think not only have you got to pass all the exams, do the refreshers ever 3 years or so but you have to have worked alongside a registered gas installer for a decent period of time to get practical experience...
all that said, with what matey was sayin above, its well concievable that a diyer with the relevant information would do a better job than an rgi....
personally i love a bit of plumbing, gets the old cells working big time, theres so much to learn...
im seriously considering finding out just how much it'll cost me to get in that position, i'd defo need to work with a real good plumber for a bit cos some of the problems you can uncover can be absolutely mind boggling...
ive been trying to suss out how to convert a pumped heating/gravity hot water system to fully pumped with the help of a bloke on another forum whos a bit of a legend... once you get your head round how vented and unvented systems work its easy enough but its like owt else, its only easy when you understand the basic principles and theres so much to go wrong you wouldnt even think about...
gas appliances are the worst...
spillage (co leaking back into the room, not up the flue) can occur for the most obscure reasons e.g. opeing a door, turning an extractor on, opening a window a crack....
rgi i know went for his refresher...
asked him to do a spillage test on a boiler, it passed, then they went for a break....
came back in the room, asked him to do it again, 'eh? just done it' - 'DO IT AGAIN!!' - it failed..... so he looks all the way round this room and in the top corner, opposite side theres a 4" extractor, they'd turned it on.... simple as that.
I had to do some emergency gas work on a job where i'd been through a pipe in the floor with the disc cutter...
rings bob, 'just do blah blah mate and ill come and test it up when im done, then you can crack on'..
so i did... no worries...
bob turns up at teatime, im stood there with him while he does the drop test...
friggin water almost jumped out of the manometer...
'f'ck me, worst one ive ever seen' he goes... looked well shocked...
now im sh'tting myself at this point and he knew it the sly f'cker...
he'd deliberately not switched the boiler spur off and the thing was trying to light...
laffed his cock off he did... but he proved a point... i didnt have a scooby doo did i?