Edexcel A-Level Mathematics

Is a Casio fx-991 ES PLUS (2nd edition) have everything needed for edexcel a level mathematics?
I couldn't find the distribution function on it (for binomial cumulative probability in AS Applied Mathematics).
Should I buy a Casio fx-991 EX CLASSWIZ? Or do I need a graphic calculator?

The ES Plus doesn't have the statistics capabilities you need. You should get either an EX or the newer CW model (I prefer the EX as it is more like previous Casio models to use). You could get a graphical calculator but you don't need one and personally I think they are a waste of money for the minor advantages they deliver in A level maths.