03 Discovery TD5 starting issue.

Firstly I apologise if this query has already been covered.
Up to a month ago, my 03 TD5 started first turn. Now it has occasionally decided not to crank. Dashboard lights are correct when ignition is turned on. Glow plug light goes out after a few seconds, but when I turn the key to crank, everything goes dead. No dash lights, no crank, just "dead". Leave it a couple of minutes, repeat the process, and she fires up as if butter wouldn't melt.
I have checked the various electrical connections, (well those I can get at), and they all seem fine.
Must be someone who has had a similar problem.....and solved it.
Thanks in advance.

Hate to ask the obvious, but when you say you have checked various electrical connection, did this include the battery to earth lead and chassis/engine mount? Maybe stick another one on - you can't have too many good earths.

This was the "first one to go to" in my quest. But I do get your point that there are never enough earth straps. But if it was a bad earth, surely it would stop it starting anytime? Still I will try anything once. Thank you.