That is the reason a full test on the installation is made when changing a cu, you are signing to say the circuits are fault free and the readings are recorded on the cert, anything found to be departing from this would be recorded on it.
I guess the answer is how good you are with your complaints proceedure, if i was in your shoes i would re-test the property so i could hold my head up and see if the results were the same, it would not be the first time that one of us has fitted a dodgy rcd or missed something in a test.
The only difference between us and builders is that we have A levels and we dont bodge it and scarper.
