So I was using the same gapping tool NGK suggest in their video even if I honestly didn't think it wasn't an ideal design:

 

 

It takes a few trial-and-errors to get to the desired gap, but this process obviously leaves some marks on the plug tip (the bent part). Now 2 out of 4 plugs look like the one in the photo while the other 2 are slightly less dented.

 

My worry is are they still safe to go in or I am risking losing the tip inside the cylinder at some point? The cut doesn't look that deep in reality and I would assume it will hold but would like to hear others opinions as well.

They will be fine, my Dad took out some horrendous ones in the 60s out of used cars he bought and they still worked fine although he replaced them 

That's not the most re-assuring statement to be honest... There's quite a difference between those engines and modern twinchargers...

Looks a bit worrying to me. Obviously if the plug is going to fail, its going to be along that fault line. I prefer the old method of adjusting plug gaps ie feeler gauge & a gentle tap on the outer electrode to close the gap. I've always had to close the gap, never increase it.

But then I'm of the age of Champion spark plugs & using a bit of fag carton to measure the gap.

I wouldn't chance it for the sake of £12

Replace it n have peace of mind. (: