I think auto hazards are only on facelift and it might not be activated on your cars. I think this can be changed in the settings menu along with the lane change indicators and the like.
As for knowing the hazards come on, the cluster lights do flash and the console button for the hazards also lights up but it only does three flashes and you can barely hear the tick tock (also another bug bear of mine, but getting used to leaving my indicators on now
) Basiclly, if you are driving hard and they do come on you probably will miss it becasue you should be watching the road and listening to Bon Jovi (the shame!)