try leaving a dish of white vinegar in the car overnight. this is really good for absorbing smells. if it is really bad you might have to repeat it for 2 or 3 nights. (the car will smell of vinegar in the morning - this disappears after a few minutes once the dish is removed and the window is opened).
i also sometimes wipe down the car seats with a water and vinegar solution - but i wouldn't try this on leather. if you want to clean the leather seats i would use a specialist product.
DH's company car has just been replaced with one from a colleague who has resigned (newer and bigger than the one he had). It's lurvely, except the previous owner was a smoker and the car smells as such. DH stopped off on his journey home with it to purchase one of those car air fresheners. However it now smells of smoke and artificial strawberry-ness.
It has leather seats so we can't use Febreeze. Anyone have any suggestions as to what we can do to shift the smell?