This i know i can help with!
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Done it to an '02 clio, an '07 grande punto and an X plate punto mk2 (Hence the "Mk2" in my name.
Anyway. All you need to do is cut (or put scotch lock clips on) the wire to the original courtesy light, 1 on the pos+ and 1 on the neg- (boot for the boot neons, and in car for the in car ones) then run the positive wire for the neon into the positive for neon, and the same with the neg. (If they are neons and not LED strips you might need to find somewhere to hide the transformer box, wouldnt know about that though, ive always used 12V LED strips!
I'm actually just in the process of doing that to my '07 Campus, but I'm running from the cig lighter and adding a switch, the same setup as there was in my X plate punto!
My idea was to put 2 x 10cm LED strips under each seat, then 1 x 15cm under each footwell, all connected up to a switch coming off the cig lighter socket. They are SO bright! But my car feels naked without them
Hope this helped!
Any more help just ask
SFMk2.