AOG - the date of 30 April is purely a legal requirement, the government are obliged to post a set date in order for the extradition process to move forward.
The fulfilment of that date depends entirely on an absence of legal argument from AQ's legal team, and of course, they are not going to sti back and let him go without a fight, nor would you expect them so to do.
The exhaustion of every legal process open to use, up to and including a return to the European Court could take anything up to two years to complete, so if anyone is thinking this is all over bar the plane ride, they should think again.