The rearmost two plugs are the most difficult to get at and I found that on more than one occasion I needed to use one of those telescopic magnetic recovery thingies, to recover the small nuts which hold the glowplug rail onto the glowplugs, after they fell into the gaps in the inlet manifold.
A 1/4 inch drive socket set was handy as the nuts I took off the glow plugs was 7mm (unusual size in a 3/4 inch or 1/2 inch set), but the ones on the new set were 8mm.
It might be a good idea to stick the new nuts onto the socket with a bit of grease before trying to put them on the glowplugs instead of trying to use your fingers. The back of my left hand is cut to ribbons
