Glow plug removal tips

[DoubleU]

Hoping I can gain some knowledge and tips before taking this on. The task - to replace all four glow plugs on my Transit Connect 1.8 TDCi without any of them snapping!

I have the new plugs. I've tested voltage to the plugs - all ok. I have a can of PlusGas and have started spraying it down the plug wells. Will keep this up for the next few days.

Any other tips for when I attempt removal? Even the threaded plug tops where the power cable attaches to are quite rusty so I think these are going to be tough...