Ive never changed the plugs myself before so Ive never really had the chance to see how bad they can get.
Im just going over the Astra at the mo changing anything that looks like it needs done.
Here are some pics of the plugs. The only one which was slightly different was number 4 (gearbox side of engine). Number 4 had a sooty style build up around it and wasnt as tight in as the others.
Better view of 4