Couple of possibilities.
Intermittent fuel relay.
Immobiliser, if fitted. I have twice had my '98 spin over on starter at normal speed, but not start. Ignition off. Enable immobiliser for 30 seconds, then off. Starts first turn of key afterwards.
Cheers,
Welcome.
I find with my T16 that the same thing that Graham reports sometimes. I also have noticed that if I turn the key to first position & wait for the fuel pump it floods & doesn't start. Mine at least needs to be just turned straight over unlike my other cars & I sometimes forget.
Were are you based WOX9?
John