Gently, is my advice! I ended up having to replace some of the little clips that secure the top of the cover to the top of the cill, plus the little clips that secure the thin upper end trim covers that go between the sill covers and the body wings (all push-fit). The wierd looking ones underneath the cill can be freed by pushing them slightly sideways with a large screwdriver in the central slot, until they pop half-loose half-sideways. Then they can be gently levered free from behind. Sounds odd, but you'll see what I mean when you try one. They are quite strong, and I didn't break any. I don't remember any problems with the end ones under the cills - they came off more easily.
While you've got the cill covers off, I strongly recommend you undo the back of the front wheel-arch protectors, as I found a mass of old leaves, mud, nests, etc stuck in there, having dropped in from above and accumulated. No rust though (only on the inner lip of the wheel arches)
Good luck!
Last edited by 1998c280estate; Oct 19, 2009 at 06:36 AM.
Reason: spelling