The wife's 2000 DI Zafira doesn't like starting now that the weather's gone cold. Even after two or three goes with the glowplug light on the dash it struggles to start. So I guess the glow plugs are on their way out. It has done 85k miles so I guess they could be tired. Do I need to change them all, or is it likely to just be one? To test them I presume they need to be removed, so if I need to remove them to test, I may as well do them all...? How much are we looking at per plug? Best from Vauxhall or will ECP be a better bet? Thanks Steve