Glad its sorted.Followed Shifty1962's instructions to cut access panel on rear floor of my TD5 90.
Job done and cover plate in place. Fuel pump now easily accessible.
Did not touch the fuel pump but used service kit for the air bleed valve on the filter housing.
No more noisy fuel pump!
Thanks for the help and suggestions.
the pipe nearest to wheel at back of fuel filter housing,should be colour coded white.pull pipe of union,carefully unscrew union,replace with part no.WJN500110,refit fuel pipe,switch on ignition,press accelerator 5 times or untill engine management light flashes on dash,repeat this procedure untill air is purged from system.
forgot to say change fuel filter also.2 or 3 procedures should expell air, you are looking for a quieter running pump if everything else is ok.
I had fuel pump problems in the past:
http://www.landyzone.co.uk/lz/f50/fuel-pump-cleaning-fault-finding-225684.html
...might help?