Don't be tempted to buy a car without first doing some research. The first thing you will need to know is what your own car is worth and what is the current value of the car that you are going to buy.
How do you do this? You do not have access to the main guide that the motor trade use so what are you going to do?
Well the first stop should be the newsagent and ask for the Parkers Price Guide. This is published each month and contains a good guide to the vast majority of cars for sale in the uk. It includes Differing prices depending on condition or mileage amongst other things.
Take it with you when you go to buy and you shouldn't go far wrong. It will give you a good idea when the car salesman tries to rip you off.