Firstly, welcome to the club mate,
Have you checked you front tyre pressures are even. This can cause the car to pull to one side...
If youv'e checked that, and it still does it, then take it back to the place you bought it, and have them check the wheel alignment. If you bought it from a dealer, you should have an AA report, amonst other certificates, to show that the car has not been damaged in an accident., so it shouldn't be a major problem.
Hope this helps......