Land Rover Repair: Disc cutting out, crank sensor, discovery td5

Question
Hi, I have a 2002 Discovery TD5 7 seater and she is giving a few shudders and then cuts out completely, no servos brakes or anything. It feels like she is starved of fuel.  If I let her sit for a short while she will after a few attempts and a bit of cranking fire up again and be on her way for 5-10 miles.  She also take a bit of cranking if she has been sitting for a while say a couple of hours or more. I am a non mechanical type but left it to a local mechanic and he replaced a fuel pump at the rear which he said had broken up and may put some metal filings into the main pump.
It is still doing the same thing despite the new pump and is a real pain and dangerous to boot when you have a tail gater and your vehicle comes to a sudden stop. She has never been run till empty in the 2 years I have owned her but could it be some form of sludge in the fuel tank or a faulty fuel cut off switch?

Any advice on where to look next welcome.
PS. To give the mechanic his dues he will not issue any bill until he gets it working right

Answer
My first thought would be to check the crank sensor.  It is common when they fail for the car to cut out or not start when warm and start again when cold.

Secondly, it could be an EGR valve stuck open.  This could explain the low brake assist.

Alternatively, the fuel injectors fail when hot, allowing no fuel to the engine.  As easy check is to remove the return line on the injectors and replace with clear hose on each.  If one fills up more rapidly than the others, it indicates a failed injector.  One failed injector would shut the system down.

Finally, if you had acccidentally put petrol instead of diesel, in would destroy the main fuel pump, as it loses lubrication.  You only replaced the primer pump in the rear.