This is a very important question, not because it's a trick to trap you, but because it addresses something absolutely vital if the legality of your extension is not to come crashing down around your ears.
When you applied for Building Regulations approval, what did you say, or tacitly/by default allow to be officially assumed, would be the way that you would ensure the electrical work would comply with Part P?
In terms of this forum, there is no wrong answer to the above, but in terms of giving you the best advice we need to know the truth.
