Hi there.
Ive got a 1.9 gti which had the same problem a while back. It came out the blue with no warning. Lights all came on but no starter motor turn over.
I didnt have time to fix it for a couple of weeks, but would sometimes try to start it now and then in the hope that it would start.
Then, it did!!
I wasnt able to find the problem as its never happened again, but i suspect it may have been the connections onto the starter motor being dirty or a bit corroded. A lot of the connections in my car are a bit like this causing lots of bad connections.
Good luck.
Andy
December 2006