Discovery TD5 intermitent starting problem

I know lots has been posted about his but I cant find any rhyme or reason to this problem im having, the air bleed valve has been replaced as has the fuel filter, pump ok, sometimes the car just starts and dies straight away, then I have to run the pump cycle 2/3 times before it will fire up, sometimes fires up first turn of the key, left it for 2 days, wouldn't start, left it for 2 days started first time, runs perfect when running, no fuel leaks, hot or cold makes no difference, runs fine all day, starting ok, then back to square one, wont start, bleed again and away we go, any ideas would be helpful, thank you.

After its started, is it happy to sit idling? or after 5-10 mins does it slow down and stall?

my 1st guess would be injector seals

My guess would be the injector copper washers (which means the seals must be replaced too anyway)... provided there's not a topside switch fault logged in the ECU but that's quite rare

Yes my conclusion too! Stalling after idling for a while is another thing to confirm it.