Basically, it is possible that even a council approved gas safe registered could be a fast tracked spotty youth with a log book listing basic competence for any conceivable plumbing or gas installation job. He or she could also have public and personal liabilty insurance should she or he forget to set the depth of their circular saw just deep enough to rip thru the t&g on the floor board(s) to acces the floor or floor/ceiling void to access and alter the f&r pipe run(s)
So that they are less likely to damage any other installation runs plumb, gas or electrical. (one day I will develop x-ray vision instead of having to 2nd guess
However, as long as the person is competent, experienced, recommended, can give you additional references (you will, should you choose to take these up ask how the 3rd party got the plumber's number, were they neat tidy, courteous and respectfull, did they hit targets vis-a-vis pricing and *timing *arrive on time complete work on schedule etc) so long as they didn't give you the phone number of their bassie mate, mum, partner etc YOU NEED TO ASK and if in doubt politely make your excuses n show em the door.
You dont need a gas safe registered person tho.... despite the issues re refilling and venting... oh and dont forget balancing = distribution system if required.
You argument (pardon the pun) doesn't hold water!
for example.... if joists need to be notched or drilled to alter the f&r pipework then surely... by your argument... you will still need a structural engineer to examine the loadbearing integrity of the floor hasn't been adversely affected/compromised
Or by further extension/exemplar you will need a joiner to access and replace the boards after the plumber and gas safe engineer has inspected the pipe alterations/joists... oh! before I forget...
dont forget the carpet fitter to roll back and stretch the carpet back into position over the gripper rods (I have a knee kicker you can borrow... (for a fee as long as I instruct you and certify you in its correct and safe use) wouldn't want a legal suit bearing down on me if you pricked your finger on the gripper.... have you had your tetanus booster!
Regardless of whether you get the council to do the job or get a self appointed PLUMBER to do the work... all you need is an experienced accredited PLUMBER adequately insured to do the work. Take note though If
If, if the plumber is called lech and hails from warsaw if it all goes tats oop you have to pay again for some1 else to put it all right!
Point noted whitespirit..... if I had a penny for allo the jobs I quoted for... was undercut by... and had to go back afterwards to put things right... cos ppp's appointed johnny foreigners to do the work after showing em my letterheaded quotes... I'd probably permanently reside in California... instead of having to tolerate the mother in laws cooking. Still back in blighty come Friday!