we didn't see 3 white lines just 2 which I believe was the umbilical cord in the way x
Talk to your doctor and see if he can give you another scan.
I'm also from the UK :) the last scan we get is the twenty week and if everything appears normal they won't offer you another scan we just deal with our midwives from now in.. that's what I was told anyway :)
Girl parts u see 3 little lines between legs. Boy parts are pretty obvious and normally they can tell difference between cord and penis. Maybe she hadn't been at it long...