you will have received a benchmark/logbook with the boiler that shold have been filled in by a corgi registered installer.it covers important things like ventilation checks, a record of flue tests , pressure testing at the meter and at your multifunctional valve in the boiler etc
are you starting to get the picture? its a service installation record to prove that what was done was by a competent person.
in the eyes of the law that means corgi registered.your fitter knows this but could,nt give a toss and has left you to put it right to prove the integrity of the installation and any subsequent srevices
what you have done is to use someone you trusted and are now having to pay again, probably ,to put it right like loads of people do.not fair is it?