Ah, so probably about the same age as I was when I was scared by the Terror of the Autons novel and terrified by some clips of that story and Spearhead from Space that I saw on TV.

I think I first saw a glimpse of Doctor Who when I was about two or three years old (this would be season twenty-three or twenty-four - I think possibly the first episode of The Trial of a Time Lord and was so scared that I didn't go anywhere near it again until I was eight!