Okay so I have been going though the issue and after 3 weeks of stuffing around I have eventually found the issue.
the code apart from the errors mentioned was fine.
The specific board I was using being a prototyping board had attached a button, light sensor, RGB Led and a buzzer has its own circuitry to make said components work.
This componentry unbeknown to my learner self was interacting with my circuit and thus stuffing the incoming pulses from the Fan Tach. Once removed both interrupts and pulseIn worked.
On a side note due to the fan only being 1450 RPM I have a far more accurate reading of my fan rpm using pulseIn and not utilising the interrupts. I know this uses the ATMEL bandwidth but currently it isn't an issue.
Regards