Grrr, finally found why i could smell diesel all the time!!
hate incompetence!!
at some point someone has had inlet manifold off i assume to change glowplugs, anyway long story short
the return pipe from the injection pump(metal) had not been clipped back properly and had been chaffing on a casting on the head right at the back of the cam cover, this has rubbed a small hole in the return pipe which leaked diesel down the back of the engine over the bell housing, hence why i couldnt find it!! every time i went out to look for it after engine had cooled down i was expecting to see a pool/puddle of diesel somewhere on the engine and never could!! engine has always been smoky at low revs since ive had it, as the fuel pressure is now correct as it isnt leaking, the black smoke has also lessened considerably, bonus!!!

in fairness to whoever did the job it was very very difficult to see it wasnt clipped in, and the leak was on the inside edge of the line, so again very damned difficult to see,
but boy am i glad i found it!! was driving me nuts!!strange thing is you could only smell it every so often,so assuming that sometimes where it was chaffing it settled just in the right place to almost block the hole!