Hi all hopefully this helps someone out.
So your 300tdi is slow to start up in the mornings you replace the glow plugs still no luck you clean all the earths and still no luck. Before going out and buying a new starter motor or a new glow plug relay try this...... locate your glow plug relay and remove. Take a thin flat bladed screwdriver and pry off plastic cover. Now have a look at where the contacts meet and you should see a build up of crap. Fold a small strip of sand paper (400 grit) and place between contacts. Press contacts together and sand away any crap. Put back together and fit. Give it a try worked for me and I saved $120nzd hopefully this can help someone out and save them self some money.

Note photos where taken after it had been cleaned and I had a big lump of crap on one of the contacts making it not get a good connection