Great! I've had the car for less than a week and its sat dead on my drive

It had a slight misfire, but was running strong until thursday, when it was missing badly....
got it home and it would run for a couple of seconds then cut out...
this has progressed to not starting at all now.....
Have covered plugs, leads, coil, fuel pump, dizzy cap, and have put another airbox with airflow meter etc ( its a K-jet 8valve) on it
Anyone got any ideas? everyones giving me grief about buying a Rotter and I'm stumped!