Hotpoint DD77 Diamond Line Double Oven

we bought one of these for a new house, by the time we moved in the guarrantee had elapsed, we tried to use it but it did not work properly, we had to call out hotpoint and their engineer had to wire up the controls (PROPERLY) he left us a list of what he had to do to the oven and said not all machines were tested at the factory, we spoke to hotpoint who said it was not their fault and that all machines were tested at the factory! (WHO DO YOU THINK WOULD LYE!!!!!!)