If you are getting it through the company, you are far better off just buying it for cash or else with an ordinary overdraft or loan. Then you can do what you like with the car. You can trade up or down whenever you like. You are not tied into any fixed timeframe.
However, I thought that people had moved completely against buying company cars. It's a while since I have looked at the figures, but it always seemed better to buy it yourself and charge mileage.
The only advantage of a company car is prestige.