Before purchasing a car make sure you have secured your finance, if you require finance. There are many finance options and many finance companies ready to do business with you.
Many offer online services which are worth checking out. You can do all you research online and then when you have decided on which finance company to use, simply complete their online fianance application form. Usually you will get a response back quicker than you think.
Then, once you have your approval, you can attend a car auction and bid with confidence knowing what you are able to afford.