(Some of my reply has been already said above, while I was drafting this post - however I have left it in.)
From your report, quite a lot is working OK. (assuming that the battery is up to scratch, as suggested above) You also mean that the car is not Cranking
, I assume? Starting
is when the engine runs.
1. Ignition key turns from posn 0 to posn 'Start' means that the key is OK, ignition switch is OK, steering lock is OK, DAS is OK (drive authorization system)
2. That means that you have 'permission to start'.
Turning the switch to the Start position should energise the Starter relay (N10/1 kS) located in the engine bay, which in turn will energise the Starter solenoid, located on the starter unit. You should be able to hear both relays click when the key is turned to Start.
If no 'click', try replacing the Starter relay. I would remove the relay case and inspect the contacts inside. For an emergency you can burnish damaged contacts with fine emery paper, just to get yourself moving again.
3. There is also a fuse 52 (15A) in the starter (M4) circuit. Check that out.
4. The starter could be toast - or maybe it has jammed and blown fuse 52. Sometimes a smart blow to the case with a mallet can free it up! If all else is OK, try that...