CTA Tools makes it easy to remove glow plugs even when the compartment is not accessible. The Glow Plug Puller Kit (7804) is especially useful in narrow engine bays, with glow plugs nearest the fire-wall. Remove broken glow plugs from the top of the cylinder head without damage.
The Glow Plug Puller Kit includes one electrode puller, one electrode reinforced drill with two guides, two specially centered mills with one mill support preventing damage to the head, one tap and one slide hammer extractor to pull out broken glow plugs, three refreshing taps sizes: M8, M10x100 and M10x125 with hex drive.
Link: CTA Tools