It all comes down to the building regulations. If your not a competant
person then you can make a building regulations application for the
installation of the boiler.The Council will probably ask for a report
on the installation from a Corgi or similar approved installer on your
work. The only bit as I understand it that you could not do under any
circumstances is connect the boiler to the gas supply. It is illegal to
work on the gas supply full stop unless you hold the relevant
qualifications