Fiesta diesel wont start when parked on hill?

Whe parked for a while, facing uphill, Fiesta 1.4 Diesel often won't start. This appears to be a common fault & it has been suggested it is something to do with the high pressure fuel delivery tube assembly. It has been suggested that the diesel drains back, so when you turn the ignition, there is no fuel in the delievry system and it needs to be reprimed. We have tried changing the non-return valve on the hand priming pump. Does anybody have any suggestions?