Is not just an American thing?
The American TV stations have seasons for everthing, like "pilot season" those one of shows that hope to get picked up as series/seasons.
"The New series of 24 is starting next week" is just the same as "the new season of 24 is starting next" is it not?
As long as I can remember its always been series, until the big shows from the US (24, Heroes, Lost etc) came along and started calling them seasons.