Hi, I have a new NEF induction hob to replace my old electric hob and was expecting a simple like for like change of wires. However the model comes supplied with 3 phase cable and I am curious as to how it is connected to my existing switch? Are the grey and black (N2/N3) ignored completely/connected if so how? If it is considered not something a competent DIYer should do then I will of course ask an electrician. Many thanks.