I had a scan at 7w, another at 8w3, and will have my 11-14w scan next week at 13w2.
If your hospital does the NT scan, then it doesn't matter whether you had an early scan at 6w or 10w - the NT scan has to be done between 11w and 14w.
If not, it's likely to depend on the reason for the early scan - my 8w one was scheduled b/c this is straight after a m/c, so my LMP is June(!), but in fact I was bleeding heavily so had an emergency one the week before in a different hospital. Even if I didn't want a NT scan, I was told they would still like to do a basic scan around 12w to monitor the subchorionic haematoma - the cause of the bleeding for the past 6 weeks.