Have you seen this pamphlet on Partner Migration? It can be downloaded from the Australian government immigration website www.immi.gov.au It spells out what needs to be provided. Download it from here http://www.immi.gov.au/allforms/booklets/1127.pdf
As regards police checks it says:
As part of having to satisfy the character test, you must provide police checks. Such
evidence will be considered in determining whether or not you can meet the character
requirements. Police checks are required for yourself and each of your dependants
(whether migrating or not) who are aged 16 years or over.
You should obtain a police check for each country in which you or your dependants have
resided during the last 10 years where:
• the period of residence was 12 months or longer (in total); and
• the person was aged 16 years or over at the time of residence.
You must provide the department with originals of police checks. These will generally not be returned to you, so you should make copies for your own records.
In undertaking character test assessment, the department may contact you and your
dependants seeking additional personal information.
If you apply outside Australia
You may need to provide this informationon page 12.
when you apply. You will be advised by
the office at which you will be lodging
your application when police checks are
required. That office will also provide you
with forms and instructions as appropriate.
Contact details for Australian missions are
I am sure that the vast majority of people don't bother with an agent - it's not a complicated process, but it does take a lot of time and you have to be very thorough. I did my UK police check online via this website Police Certificates