Update: Right, I plugged the ole manual code reader in and got a P0405 code (don't know why all the mechanics with their scanners all said no error codes), which seems to be something to do with EGR sensor.
So, my plan, from collecting all suggestions so far is: clean the EGR valve, clean the MAF file, Try to start and keep it running for more than 10 seconds. If that fails, try and find which of the 5 wires to the fuel pump is the live feed, and run it direct from the battery to the pump bypassing all the electronics. I'm tied up for a while but should be able to have a go next Wednesday.
Anyone got thoughts on the plan? I'm hoping if all else fails the direct feed to the pump may keep the engine running, though from reading the replies I am not keen on that.. One thing I can't check could be something simple like the fuel pump hasn't got enough pressure to keep fueling after the engine fires, but I guess only way to prove it is to change the fuel pump.