I work in lending, but not personal loans. (Business equipment finance).
Every lender out there will have different criteria, but as Tweety said generally 3 months. Van also vary depending on the amount you wish to borrow. Best to ring around various Banks, Building Societies and Credit Unions and check their criteria, starting with who you bank with at present.
Normally the easier the lending policy the higher the rate will be, so if you go through a cash converters type loan you will probaly be paying a very high interest rate. So make sure you get all teh details inc rate upfront, which under the credit laws they must give you.