Domestic gas pipework question

[staffordian]

I suspect the answer to this is "it depends', but I thought I'd ask it anyway.

The gas supply to our 1970s bungalow enters the meter box through the cavity and the original pipework beyond the meter again goes into the cavity. Somewhere in there, it branches to a capped pipe (original 15mm pipe to the old boiler), a second capped pipe which runs under a concrete floor to where there was once a gas fire, and there is also a branch supplying our gas hob.

Finally, a new 22mm pipe is teed off the pipe emerging from the meter itself, which comes out of the meter box in a sleeve and runs up the outside of the house wall and into the loft to supply our combi boiler.

I want to eliminate the old pipework for two reasons. First, it's condition might not be great, but as most is hidden and inaccessible we would only know there was an issue when we smelled a leak.

And second, but less important, we cannot have a smart gas meter as the fitter said he was not permitted to install one where pipework was hidden in case a joint was disturbed and could then not be repaired.

So, finally, the question...

Can a new 15mm pipe be teed off the new 22mm pipe supplying the boiler, and routed the short distance (about 1 metre) along the outside wall then through to the hob, or would the 15mm pipe have to come off the pipe exiting the meter? I can't see that it would make much difference either way, but would taking it off the new 22mm branch for the boiler supply risk reducing the pressure at the boiler more than if the supply branched from the meter pipe below where the new 22mm pipe tees off?

We've someone coming to quote us, but I just wanted to be prepared if possible. I'd be annoyed if he said it was fine then some time later, a boiler engineer disagreed...

Any thoughts welcome.

[jaizan]

My house has a 22mm pipe feeding the boiler and a 15mm pipe teed off that to the gas hob.
It works and was done by a suitably qualified & registered person. It has passed gas safety checks since installation.

[staffordian]

My house has a 22mm pipe feeding the boiler and a 15mm pipe teed off that to the gas hob.
It works and was done by a suitably qualified & registered person. It has passed gas safety checks since installation.

Thanks very much.

Exactly the sort of practical example I was hoping to hear.