So replacing the fuel pump turned out not to be the issue with the Defender cutting out when under load. Tomorrow we’re back on a tow truck and off to a Land Rover specialist. Unfortunately the cause is still unknown and I simply don’t have the test tools or know enough about this engine to narrow it down any further.
Fingers crossed it doesn’t end up too expensive to repair. We sure could have done without this especially with only a few weeks before our departure date.