1.2 polo 2002 starting problem

I hope someone can shed a little light on the following. I could not find anything similar in the FAQ section but if present please send me in that direction.

I have a 2002 1.2 polo petrol 3 cylinder ( 78000 miles) and it is refusing to start. This happened after I started the car from cold and it fired but I was a tad quick in letting the key return to its default position and it stalled. Since then it has just refused to start. So far I have checked:

1.Fuel pump - it is whirring and making noise when the ignition is turned on. The injector rail (rack?) is pressurised with fuel ( when I took the end cap off fuel squirted our under pressure).

2. Sparks are big and fat.

3. Local garage came and did a diagnostic on it and nothing showed up. The engine management light goes off after the initial run through check after the ignition is turned on.

It has been suggested to me that the timing chain my have jumped- is this possible!!!!!!!!!!!!!. To get that checked I am told the head and sump need to come off and I am looking at about £350 to get that done.

So, has anyone any ideas - am I missing something very obvious.

Thanks for listening. Any any advice gratefully received.

Stephen