Vectra 2.2 diesel estate?

My partner bought a second-hand Vectra yesterday, he is no fool and checked everything on it worked and also took if for a test drive and it was fine. We drove for 140 miles yesterday around London and stopped at Bluewater for a couple of hours and all seemed fine until this morning when it wouldn't start. The battery is currently on charge as it was the only thing we could think that it was. My partner is a typical male and pressed lots of buttons on the dash, could he have possibly put the immobiliser on inadvertantly? I would have thought that the central locking would have over-ridden that though. Anyone have any ideas on what it could be? We have lights, radio etc and the engine just won't seem to turn over. Thanks ;)