Back of engine (looking from the front), if I can remember rightly. You have to take the coil packs off to get to plugs. They just unclip from plugs, large black plastic looking item. It may be retained by a few screw or bolts, which are easy to get to from top of engine.
Found this pic:- http://vne-resource.iol.co.za/30/picdb/article2/3/2/26771
Hope it helps? Just above the citroen badge on engine running parallel with top of engine, long black plastic object. Plugs are underneath that.
George, August 2007
