Purge cycle is with ign on, press accelerator fully 5 times. Engine management light will flash and run the cycle to purge air from the fuel system.
Not a difficult job. How To on UP's site here
http://www.discovery2.co.uk/Injector Seals.html
Griff
Yes there is a none return valve in the fuel filter housing. Rear outer if I remember, but please check. Does it start after doing the purge cycle? If so I suspect its the injector copper washers. Plenty of info if you search.
Griff
You have 2 seals on the injectors. Bottom copper one will allow combustion gas into fuel and cause starting issues, Rubber O ring seal will allow diesel into oil and cause oil level to rise on dip stick.
Griff
Have you tried starting it after dong a purge cycle? If it does then there's air getting into the fuel system and may need the injector washers/copper o rings renewing.
Griff