ETOPS
BOAC,
I would suggest that you're not entirely correct. The worst case is Depressurisation plus Engine Failure is it not?
For all the others, yes you can divert at any speed you like but as BOAC says don't run out of fuel. You can also divert to any alternate you wish - not necessarily the planned ETOPS ones. And your actual divert time may well be greater than the ETOPS time that your company has approved. Remember, in most cases the normal fuel covers the ETOPS requirements as well.
The "Getting to Grips with ETOPS" document is an excellent guide as are all the GTG books - regardless of what aircraft you fly in this case. (never thought I'd compliment an Airbus Manual!!)