Creamie, I am presuming it is your GP who determines if "you have one of the disqualifying conditions". In practice (I haven't tried it yet), it would be interesting to see how many GPs would actually be prepared to "sign on the dotted line" if you requested a "drivers license medical certificate - aviation".
From the CASA website...
Medical examination
You will need a driver licence medical certificate (aviation) confirming your fitness to fly, issued in accordance with the conditions in Instrument CASA EX 68/12. When applying for this medical, you must tell the doctor of any condition that may adversely affect your ability to fly safely. Examples include but are not limited to diabetes, epilepsy, heart conditions, stroke, eye problems (such as cataracts), psychiatric disorders, blackouts or fainting.
The certificate issued by a medical practitioner uses the uniform Australian private motor vehicle unconditional driving licence medical standards contained in the Austroads Inc. publication Assessing Fitness to Drive for Commercial and Private Vehicle Drivers, but modified by additional CASA-designed medical standards. This type of medical examination can be undertaken by any general practitioner and is similar in form to the Austroads Inc. driver licence medical examination.
It's interesting to note the length of list of disqualifying conditions for normal class 1 to 3 medical in the USA....
Unless otherwise directed by the FAA, the Examiner must deny or defer if the applicant has a history of: (1) Diabetes mellitus requiring hypoglycemic medication; (2) Angina pectoris; (3) Coronary heart disease that has been treated or, if untreated, that has been symptomatic or clinically significant; (4) Myocardial infarction; (5) Cardiac valve replacement; (6) Permanent cardiac pacemaker; (7) Heart replacement; (8) Psychosis; (9) Bipolar disorder; (10) Personality disorder that is severe enough to have repeatedly manifested itself by overt acts; (11) Substance dependence; (12) Substance abuse; (13) Epilepsy; (14) Disturbance of consciousness and without satisfactory explanation of cause, and (15) Transient loss of control of nervous system function(s) without satisfactory explanation of cause.