One of the trickiest aspects of learning a new language is the pronunciation. For your A-level speaking exam your pronunciation doesn't have to be perfect, but it does have to be clear. Here are a few steps you can take to get your pronunciation tip top. Firstly, when you learn a new word, make sure you learn how to pronounce it properly. A new online dictionaries offer a recording of the word said by natives. I recommend https://www.wordreference.com/es/ as it offers various pronunciations of most of the entries. Secondly, as Spanish is a widely spoken language, I recommend picking one variant. Think of which type of Spanish you hear most. Does your A-level teacher have a European Spanish accent? Or are the majority of your resources in Latin American Spanish? Focusing on one accent will help you pick up the set sounds more easily. Finally, remember that learning a language takes time, especially to an advanced level. Make sure you expose yourself to native speakers everyday. I recommend listening to a radio station from your chosen Spanish speaking country (try Cadena dial if you are focusing on Spain). Mucha suerte.