Loss of power on td5 06 plate but comes back again while driving

Hope someone can help me here, I own a Td5 06 plate, the other day my wife had taken it to work and the landie cut out and lost all power…..after a lot of chew thinking it was the battery on the fob as the doors would not open, I finally found out it was the crank sensor, changed out and after the third time turning over it stated, now from a landie that started first time on the turn of the key it takes about 3 or 4 goes and having to put my foot on the accelerator……once going it seems that the power dies off while driving then picks back up but is starting to get more frequent……you can hear the diesel pump work when turning on the ignition …..any ideas, am stating to lean to the fuel filter but just changed this out about 9 months ago.

Had similar symptoms tracked it down to the yellow relays under the drivers seat they weren't correctly seated I swaped them about.Would start with the easy options first and check for oil in the red ecu connector when in there.

It's pretty cheap to change the filter so best to start there.
Just because you can hear the pump doesn't mean it's putting out enough pressure.

Ok all have changed the fuel filter and have gone through the sequence of bleeding it through, started up no problem and took it for a spin everything seemed fine then got 1 mile down the road and the engine died no warning lights just totally stopped running……after about 5 minutes I turned her over and the engine started got half way back to my house and did the same engine died again, waited another 5 minutes and started up again and got back home. I am starting to think there may be air getting in the system and were going to start looking at the injection system any thoughts.

Have you checked relays under the seat?
It's also not unknown for the ecu to play up.