Yes, you are permitted to use a calculator in the JAR exams.
Unfortunately the CAA rules concerning the acceptable types of calculator are all a bit ambiguous. They must not be progammable in the sense that you must not be able to pre-progam them with lots of equations.
Although the rules also say that they must not be alpha-numeric, almost every calculator in the shops these days is alpha-numeric. The CGIs have asked the CAA to provide a list of acceptable calculators, but they refused to do so.
On very rare occasions studunts have had their calculators confiscated. The best option is to get a CASIO FX83MS. This has all of the functions you require and is used by a very large number of students, so if you are challenged by the invigilator just ask him/her to check what all of the other students in the room are using.