9n3 bits on a 9n?

Hi everyone, I drive a 1.2 litre, 52 reg polo 9n three door. I am 22 years old and have held a clean driving licence for just over 4 years. I have always wanted to do a few things to my polo but I was unsure if it would make my insurance more expensive and what I would need to declare. One thing I have always wanted to do would be to put 9n3 rear light clusters on instead. I would also like to fit 9n3 seats as I learned to drive in a 9n3 tdi which had much nicer seats than the base 9n. I was wondering if these need to be declared or if it's okay as long as they are VW bits for a similar model. I would also like to upgrade the sound system to something I can plug my ipod or phone into (at the minute I just have the tape with an aux cable in it) I remember a friend had to declare a set of cheap £20 speakers from halfords in his 107, I expect I would have to declare a sound system upgrade, but how much would it affect my insurance?