Probably just focus on passing your GCSEs?
Remember to become a psychiatrist you need to do a medical degree covering the whole of medicine, then work as a foundation doctor for 2 years across the whole of medicine. You won't start specialising in psychiatry until 7-8 years after you finish your A-levels, so you need to be motivated by the whole of medicine and not just psychiatry. Also I gather the key thing that separates psychiatrists from other mental health professionals is their knowledge of the rest of (physical) medicine and how that integrates with treating mental health conditions in various contexts.
So just do well in your studies, do the general healthcare work experience expected for medicine, and read any of the wide range of books which are relevant to medicine (whether specific to psychiatry or not - and some of the less explicitly psychiatric ones may still be quite interesting to you too!).