On really cold mornings or after the 90 TD5 has been standing for few days it is becoming difficult to start. It fires and then dies. After a couple of tries it kicks into life as if nothing has happened. Any ideas? Is it fuel pressure or glow plugs. Any experience greatly received.

 

When was the last time you serviced it? Like replacing the fuel filters. I don't know about the TD5 but a 300Tdi in good shape will start at below freezing temps with no glow plugs at all.
Very few TD5's are in the US, where most of this forum's members are. For that engine you'll have better luck on a UK forum like:
Land Rover UK Forums
or
LandyZone - Land Rover Forum
Or the Australian forum
http://www.aulro.com/afvb/