Bleeding the fuel head is always a good starting point but keef says the fuel head and filter are new and the problem did not go away. While I'm not sure I understand "It will now die after 10 -15 mins idling on the drive" (that US vs UK english language thing I imagine) I note the comment about it dieing when backing off the throttle combined with a wait of 10-20 minutes for a restart which implies this happens on an engine that's at operating temperature. That suggests to me a possible heat induced sensor problem that goes away when things cool down.
There are at least 2 posts (
viewtopic.php?f=5&t=64199&start=80 and
viewtopic.php?f=5&t=66905) about similar problems that were traced to heat impact on the crank position sensor. A quick glance at 2.5L CRD FSM stuff on Sir Sam's NOOB site indicates that this sensor is on the 2.5L engine.
Worth checking as the diagnosis test is a pretty simply one.