It does depend on the bank, but if you have dropped in income they will take this into account in regards to how much you an borrow.
It is also hard for them to use casual wages as it is not considered guaranteed income but if you have a history of working so many hours per week, they may be able to use it.
Interest rates have reduced since you last borrowed so that is a positive as far as how much you will be able to afford and the history on your current home loan (given you are so much ahead) will also help with the loan application.
Depending on your parents wages and whether they work or not may also help you. For example if your parents are 80 years old and living on the aged pension - the bank may not consider them suitable guarantors. If they are still working fulltime and middle aged - it would be better.
Hope this helps, each bank is different though so I am just basing this on my past experience.