hi mate, welcome to allcorsa
first of all, nothing wrong with 5 -door corsa's whatsoever!
some people dislike them, but on the other hand some people prefer them, bcause they're less common than 3 door models
if you look here
http://www.allcorsa.co.uk/forums/showthread.php?t=28
yo will see my old corsa, which was a 5 door, a few simple but effective body mods, and it also had a 2 litre fitted.
if you want to go down the road of bodykits etc, everything is pretty much the same as the 3 door, with the exception of the rear arches, and some sideskirts (due to difference in shape of rear arches, and some sideskirts join onto rear arches) and also the tail lights are different on a 5 door!!
hope this helps
feel free to ask anymore questions you may have, post some pics of your car too if you have any