Thanks for all your advice! I relation to the gym supplements - I hadn't decided to definitely take any, I will take all your feedback on board, I just wanted to get it checked out anyway, the more important thing is the hayfever medicines.
Niknak suggested above contacting the CAA medical branch - is this something that I can do before starting with NATS? (I am not due at college until July) I cannot find any specific details for this on the CAA website other than just general advice. Is there anyone I can contact at NATS? Is the medical department at NATS able to give this advice? If anyone has a contact number for them I would appreciate it greatly!