Thanks for the advices.

Headed under the bonnet - checked all earth straps and other wiring. Eventually discovered that there is no power to the ignition wire to the starter. A by-pass gets a result from the starter motor.
but why???

I am thinking relay - but it clicks, which generally means its ok - or back to the immobiliser theory????

Any Other Ideas??

I had this problem, under the dash there is a thing that looks like a spider, 4 wires in each side. One of them is starter motor related - it goes to a relay first - one is fuel and some other stuff, find the one that is the starter, or even one that is dead when you turn on the ignition and thats the one causing you the problem.

Take it off and put it round one of the other ones (on the same side), the engine should now start. If it does, then solder it onto the other one, all it means is 1/4 of your immoboliser now isn't functioning!