I changed mine over to MG ZS side skirts and it was a direct swap. They are easy to remove for painting, from memory there was I think 2 self tappers in the front wheelarch, remove these, underneath there are I think 7 "scrivets"
these are plastic and have a centre screw which you undo then the scrivet will drop out (if you want to see what a scrivet looks like open your boot and look down on the rear bumper there are some there). Once all the scrivets are removed the sidesill will slide towards the front of the car, you may need to tap it at the rear. Once it is slid forward it should come off its locating clips,(Note which way up they are) you need to remove these clips, turn them diagonally and they should come out of their holes. To put the sidesill back the clips are put in their holes in the sidesill you then push the sidesill directly against the side of the car and push the clips into the holes, refit the scrivets and fasten the self tappers - Job done..
Scrivets are 30p each in packs of 5 from MGRover/X-part.