As important is how you finance it.
Often a dealer makes more out of arranging you a leasing/loan deal than out of the vehicle.
If you have spare cash then buying outright is prolly the best way - if not, and you have time get a loan "in principle" in place from your bank as this will probably be cheaper than the dealers finance.
Also be wary of "loan protection" and "insurance shortfall protection" too - if you want to know more about these then I can give you a layman's view.
The difference between say £145 a month and £175 a month doesn't seem a lot but over say three years, you've spent an extra grand or so.