Be careful, I had the very tip of some glow plugs breaking off before.
The Glow Plug body comes out Ok, it’s just the Tip that’s stuck in the Head.
The Tip swells/mushrooms after a few years use.
What now, Head off?
No, some say the Tip will pop out if you start the engine.
I rather do it the old fashion way:
Take the Injector of the effected cylinder out, and bring the Piston to the top by turning the engine over with a 19mm Socket and Retched.
Now use a small Punch or Drift and knock the broken off tip into the engine.
Use a Magnet probe or similar to “fish” the tip out of the engine true the Injector hole.
Refit the injector, and the new Glow plug.
Been there, done it, but never got a T-shirt..