My mate has a C reg 1.8 GTE 4 door.
When you can get it started after loads of turning over it runs for a couple of minutes then cuts out?
When ya try to restart it theres no spark.
Advanced the timing and it started retarded back to 1000rpm and a couple of secs later it cuts again.
Check to see if the ignition control unit is full of water. Had a very similar thing with my GSi Carlton last week, and it turned out to be a blocked drain swamping the unit. Replaced it with one from a breaker and bingo. Make sure to clear blocked drain as well.
(It is mounted up near the wipers on a Carlton. Not sure with an Astra.)