Corsa b 1.2 (2000 Reg) Wont start :(?

Hey My freind put the Battery the wrong way round on my corsa 1.2l petrol Car its a 2000 Reg
The things i have done

1. got new battery
2. cleaned Engine
3.checked fuses (all are fine)

All the electrics work horn indicators, the doors lock the alarm works everything just when i turn the third notch to start the car it turns over and keeps turning over doesnt start i can smell petrol through the exhaust and yes there is petrol in the tank I dont wanna spend alot of money to fix it , it worked before the battery was put on the wrong way so i hope somebody out there can answer my question
Im on windows live messenger now: magot_12[at]hotmail.co.uk or Just leave a reply thanks
Josh