Would faulty or blown glow plugs turn the exhaust management light on?

AFAIK yes it will give EML on dash

Cause the light came on and I had a diagnostic and it said glow plug. But then the light went off straight away and now a day later it's come back on again. So I didn't want to jus change them if that's not the problem because the car seems to be running spot on.

Glow plugs don't affect running, only starting. My PD150 started all through the winter two years ago on 3 plugs so it'll probably be fine, but they're only about £8 so might as well get a new set...

As above, get new set and see how it goes.

cheers guys, just got some plugs ill fit em at the weekend