99% sure you're not gonna be allowed a texas instruments graphic calculator in your exam so dont waste your money. the exam boards are actually surprisingly strict about what calculators are and arent allowed. you can check this however as it may have changed with the new specification
if you want to upgrade to a smarter regular calculator thats cool although maybe wait a few weeks and when you see what sort of functions you really need and have had a chance to see what calculator everyone else is using