If you have had the 8 week scan I would go with that - though I'd be tempted to take the other because it brings it forward!!

I had a dating scan at 5 wks and they said today at my 12 week scan, that I measured about 3 days earlier, but they wont change it as the earlier scan is more accurate.

I cant go by my LMP as I ovulated so late, but I know when I ovulated and goign by that I should be about 11 weeks today - so I won't be surprised if I go over the due date. (Fertility Friend knows best!)