They are generally not really interested in being impressed, because that should be the norm!, however if you remember some of the more obscure numbers or formulae to be able to quote this may help. (not too obscure because they will not ask that), but if you know the BS7671 value of max Zs for a 40A breaker it may come in handy, especially if you are doing a shower. I remember one inspector asked for the length of time records of notifiable work should be kept be the electrician and he was surprised that I knew it was three years.