I've bought two new cars this year. One has been a disaster, the other so far good as gold. I'll write more later when I'm not on a phone!
Car #1. Mercedes, 05 plate bought from a Merc dealership. They sold it when new to a 'lady owner', she had it serviced by the dealer at the correct intervals and was the only owner. Below average mileage. Should have been a no brainer. In 5 months of ownership, its been back to the dealer once a month for various faults. Bane of my bloody life. If I hadn't have had the foresight to pay for a warranty, it would have cost me £2k in repairs already.
Car #2. '02 plate Volvo, high mileage, no service history, 5 owners. Its been great so far.
My advice? Ignore service history and milage. Take it for a good test drive and have the AA or a friendly mechanic look the car over. Take your time, there are loads of motors about, don't rush to buy one.