Hello Shaun, bit of a risk but I’ve removed the tip of the glow plug a couple of times like this, (in desperation)! Move the piston away from t.d.c. & with a perfect size pin punch knock the tip into the cylinder (they’re hollow & very thin walled). Remove the injector, turn engine till valves are shut on that cylinder, put air blower into glow plug hole & hopefully catch the tip as it comes out of the injector hole. Worked every time for me (so far).