I recently had an Easee one charger installed, I had to pay an extra £250 for the install. I needed my water and gas bonding as they where missing , also needed an extra 25m of cable as my consumer unit is towards the back of the house.
Depending on the age of your house, but newish homes have plastic or plastic sheathed pipe entering the home with water especially not needng main bonding as per wiring regs. I do find some installers like to make a quick quid or so. As said it depends on the age of your home and what type of pipework enters the home.
I forget who, but someone on here had to correct the installer or NG but, cant remember which.