Any advice for my 300tdi not running right?

Hello all. I have defender 300tdi hi-cap.
Problems started about two months ago when giving her a standard service. Since then it takes a lot longer to start than normal, a good 5 seconds of turning over before she fires, previous was nearly instant.

Anyway, once she was strarted ran fine. About week ago, i dont know if the problem is linked, but now she runs really crap, driving along seems fine (possibly a little less power) but when i come to a junction to idle, she runs really poor, put foot on throtle and takes about 10 seconds to build up revs, sometime it stalls, and the stalling is getting more common. Cant really drive it now.
Didnt seem to be any pressure in the fuel primer thing, so bought a new one (lift pump is it?) and thats made no diffrence.

pretty stuck on what to do now, no one seems to know.
Any advice or help would be so helpfull

Thankyou so much
Dan

My friend said to check the pipe after the turbo for oil to see if the seals have gone, welll, ive checked and yes there is oil, so im assuming i need to replace the turbo, but would that cause problems that ive mentioned?

undo front banjo on injection pump and pump lift pump to see if your getting claen air free fuel to pump (you may need to click engine over on starter in to get pump to work), i would think you have poorly lift pump ive had new cheap ones worse than the old or air leak ,there is allways oil in turbo pipes to and from intercooler so this is probably normal as long as loss isnt noticeable on dipstick,pipes at tank are steel and rot ,putting apiece of clear plastic pipe in between filter and front banjo on inj pump is good way of diagnosing faults in system or not as some times air is only drwn in at higher revs