apatia,
I think we had exactly the same problem with my g/f's Polo. Hers is a 55-plate 1.2 64PS model, petrol. The lights came on on the dashboard as normal, the car would crank but wouldn't catch. I tried jumpstarting it, in case it was some sort of voltage issue as I had no idea what her starter motor sounded like. Still no joy.
Eventually whilst cranking I pumped the acc. and the car kinda spluttered. This seemed promising so I started pumping the pedal rapidly and after a lot of spluttering the thing actually started. It has been running fine ever since.
A bloke at work has an 07-plate 1.0 Polo and has reported the same problem. Maybe they don't like being left out in the cold/damp!