The worst thing is that, given that some of the pipework (for example the tidy parallel pulled bends in the first photo) is actually quite good, it seems that this installer does actually know how to work to a good standard.
Regarding making good, plastering and painting can be a grey area, but leaving a hole in the wall, particularly when in close proximity to a boiler flue is neither acceptable, nor safe.
The installer of a boiler is required to carry out work to the standards imposed by legislation and by the boiler manufacturer. Being a registered and qualified installer, he has shown that he is aware of this. If he's going to charge gas installer rates (which he clearly has), he needs to work to the appropriate standards. What he has done is contempt for the customer - he happily took the money but was going to leave that job half finished and see if he could get away with it!