Thanks mate very informative!!
The other option on the insurance was the 258bhp which I'm now guessing is the original N52.
So I'm also guessing that the N52k that is in my car is a middle ground between the two?
I will still use the 258bhp for insurance as in my eyes the N52 and N52k are related and I deffo don't have an N53.
Have I got any of that wrong?