Sorry for the late reply. I found out after contacting my insurer (Admiral) and they said that i still had to inform them and that it would likely affect my premium. I had a friend who's insurer said the said thing, i can't remember who he was with, i'll ask him when i see him at the weekend. But yeah i was a bit surprised myself as i thought the same thing, take the course and avoid the extra premium but it looked as thou that wasn't the case. Unless i was lied to by Admiral but i wouldn't say why they would?
Edit: Forgot to say the reason they said i had to inform them was because, irrelivent of whether i got points or not or the offer of the course, the fact remains that i still broke the Road traffic act therfore they had to be informed.