The medicals can be done using any panel doctor in our area from the following list at the link below
http://www.immi.gov.au/contacts/over...el-doctors.htm
You can download the forms needed at:-
http://www.immi.gov.au/allforms/pdf/26.pdf
Our cost was £140 each and you need to take your Form 26, with a photo attached to the top and your current passport. For the blood test you don’t need to fast from food intake
Then there's the chest X Rays, these are usually done seperetly and the forms needed are at:-
http://www.immi.gov.au/allforms/pdf/160.pdf
Our Chest X Rays cost £80.50 each. Make an appointment and get these done a week or so before your Medical. They then get the chest X Rays to your chosen doctor and he can then finalise all for you and get them sent off after your medical. It sounds more complex than it is, its easy really just need to tie up the dates close together.
Hope this is of some help to you and wish you all the best. Good Luck:)