Had to remove 4 x glowplugs from my TD4 2005 recently.
None moved and I know, from a bench test of a broken one, that they snap at 30 ftlb.
I didn't want to break them so trawled for techniques that might work. This one looked reasonable and it...
https://www.lrparts.net/lr001127.html
there is also autodoc, this is for the swedish site but there is also a uk side to them as well not sure if they have the part but you can try...