Right, so I lost it as a daily so haven't been able to look further into it. However, I dropped a car at mechanics before and gave him the symptoms. He basically said he'd not even bother pulling the glow plugs as it sounds like the lifter pump (or something similar, memory sucks) will just be draining back. 2.5k-5k to fix. So it sounds like it's just going to be lived with as that's not economical to fix really considering 4wds value. It's not a big deal really. If it's driven every day it starts ok, it's just if it's left longer that the problem occurs.
Just thought i'd post this on the end anyway incase someone uses search. So that's the result, though not guaranteed, pretty safe bet for this case.