Perhaps you didn't intentionally portray the numbers in this way, but your post reads as if to suggest that 40,000,000 people in the UK looked directly at the eclipse in 1999, and only 70 of those people got significant eye damage.
Hopefully, you understand that in 1999 (and 1996) the expert advice not to look at the eclipse was readily available in the media - this isn't something that became known later, due to the internet. I was a child at the time and it was drilled into us, I remember making the cardboard viewing boxes in school.
I'm not sure where you got the 40,000,000 number from, but that's nearly 2/3 of the UK population at the time so I'd guess it's an estimated number of those who in some way "watched" the eclipse in 1999 - but "watched it" does not mean that they looked directly at it with no protection. I "watched it" myself through a (safe, strong, certified) welder's helmet that my parents put on me.
I don't know how many people looked directly at the eclipse with no eye protection in 1999 but common sense says it wasn't 2/3 of the UK population. So if you want to calculate the chances of getting eye damage from looking at it without protection based on 1999 figures, you'd be better off going with a number of 70 out of however many looked directly at it back then, rather than 70 out of 40,000,000 who participated in the event in some way.