Thanks for these replies.
Just to turn the question round a bit (should start a new topic really but hey..
):
What is the minimum FLEX on the A320?
Relative to SAT I assume? Presumably there comes a stage where the FLEX temperature is so close to ambient it makes doing a FLEX takeoff a bit worthless.
For example, OAT is +35 C @ MSL on a nice hot day (somewhere other than the UK). Could you do a FLEX 40 takeoff on the A320 in those conditions, or is that really just not worth it?