IIRC, with Bupa, before the medical starts there is a question form to fill out that asks about your medical history, time off work and general sickness etc etc
The ECG is dependant upon your employer and the company performing the medical. I had a railway medical last year and the ECG was not required.
You will be asked what medication you have taken two weeks prior to the medical. Declare EVERYTHING, even over the counter stuff...its better to be safe than sorry. If you are taking (or have taken) perscription drugs, take any packaging with you so you can give them the details. Theres no point trying to hide anything because all we become clear once you have done the urine test.
It sounds obvious, but Id suggest not drinking (alcohol) at all at least 12 hours before the medical.
You will be tested on colour blindness as well as your general eye sight and of course your hearing too.
Blood pressure, weight and height are all recorded.
Its all pretty straight foward, nothing to worry about.