Rover 75 fuel pump in tank

hi I have just bought (privatley) the rover 75 2.0 diesel on 2002 plate and have run into problems within a week I have searched many of the forums on here for a solution and think i may have it but need a little help!!
firstly the car is a lovely car which gave me much pleasure for the first few days until started having intermittent starting problems but solved just simply by either taking the key out and trying again or applying a little pressure to the accelerator then one day just wouldnt start whatsoever until i put a about 4 gallons more diesel in and pretty much started straight away then about 15 miles later wouldnt start so i tried more diesel again but no good
from info from the forums i checked under bonnet pump seems to be working humming away making slight vibration unplugged the output that goes to the filter and deisel flows out not very strongly though and seems as its heated, as for the in tank pump no noise except for the sound of fluid dripping checked the voltage its ok around 11 to 12 v so took the pump out altogether the tried nothing its dead it seems removed it from the housing and have the part number on it: 136 02 k124 where do i get this from ?
also checked the ecu for water damage seems bone dry except for small amount of corrosion on bottom screw
fbh kicks in every time open door or unlock car lift bonnet etc dont think thats working
tried easy start in air intake while cranking it started
thanks for any help