Calculating and planning for new heating systems and inspecting them after they had been installed, to make sure they were to specification and standards.
Well I certainly wouldn't work for that organisation as an installer. I would want the system to be designed by someone with a lifetime of experience instaling. And I wouldn't want you inspecting my work either.
Anyway as a sercice engineer I get plenty of opportunity to see installers work. The best work is done by independents who plan design and install their own work. The worst is by companies like you are talking about, they put in such diabolical faults like not providing a pump overrun not gas pipe sizing correctly not range rating the boiler (not always necessary but it's madness to leave a 28kw system boiler at 28kw in a two up two down or a mobile home, and I have seen it twice now. I mean it's the wrong boiler as it is but not to adjust it is total ineptitude.
There are so many factors and pitfalls you can't possibly design systems without plenty of tools experience.