Christening, baptism? what the heck is the difference, some bloke who wears his collar back to front splashes some water on you, recites a spell prayer and it is meant to mean something?

Technically "baptism" is the rite in the Christian Church by which immersion in water symbolizes the washing away of sins and admission into the Church, whereas "christen" is to name (a baby) at baptism as a sign of admission to the Christian Church.

They are generally used interchangeably.

It appears that when I was christened, I was actually baptised into the Church of England :_|