Take this to a cheap garage and ask them to look at the LOW TENSION FEED - a small piece of wire attached to the starter motor underneathe the engine - it has probable come loose! I gurantee that it is NOT the immob.
You may be able to get to this yourself if you jack it up on one side - look for a small black push on clip - this will probably be loose - wiggle it and you should be able to start the engine.
I had the same problem - called out mechanic on a SUNDAY and he did it 4 £30.
Oli - seeby1978@gmail.com (if u need more), August 2005