Substandard shower installation and cracked walls

The shower (that I purchased) has been installed on an un level shower base so it does not fit properly against the wall. To rectify this vast quantities of sealant have been used which needless to say has become holed and leaks water out onto the floor. The shower appears to have been glued to the wall with the stuff and my smart glass is smeared with it too - it doesn't come off.<br> What should have been a beautiful shower unit looks terrible and does not do the job it should be doing. Further huge cracks appeared in the wall that was also plastered by the same builder. I myself have had to fill and repaint these. The work is fully paid for. The builder also owes me a certificate for the sliding doors installed to satisfy building regulations. My emails go ignored. He says I didn't report the poor installation on the day they finished work there. I did, to his son who was the overseer onsite. I shouldn't have to report failings anyway, he should have been there to carefully check the work himself which he did not do, nor has he been back since to look. I have sent photos so he can't say he doesn't know about it.