SiFu Bennett began training in martial arts in 1986 and experienced several styles before finding Wing Chun in 1999. Since then there has been no looking back.
Within your own school SiFu (師父) means your teacher with specific reference to the family line. So for example, SiFu Bennett is the head of Natural Wing Chun therefore his students should refer to him as SiFu.
If referring to an instructor, from a school other than your own, as SiFu (師傅) then this would have a different meaning and is more of an honorary title referring to their high level of skill. In China for example this term can refer to a cook, mechanic, artist etc that is highly respected for their craft.