Hi, honestly in my experience I didn't do anything. It's all luck and a patience game depending on existing staff leaving/dismissed.
Regarding Medical, a recruiter will email you asking for your availability to do it. You will be booked an appointment by the recruiter at one of their private healthcare centre mainly in central London to perform some tasks (breathlyser, Urine, Hearing & Eye sight) with a series of questions on your medical history. Then after all that, more waiting for a phone call from the recruiter for an available position