loveulots I think it should be reasonably obvious at 16/17 weeks - they will caveat it anyway. The place I've been (privately) for some scans has a 100% success rate from 16 weeks. And they get you to come back if they can't tell first time around. I had the harmony test so know already, but still tempted to have a scan at around 16/17 weeks unless little lady starts kicking loads as I am still massively anxious. I have my "20 week" scan at 19 weeks, so not that much longer to wait really, but still stressing Lovely birthday present idea for you dh 
sleepy it's a bit blurry but looks quite boyish to me according to my limited google research I think it's rounded for a girl and for a boy a flat forehead, more or less square-ish lookin head. Think the science is a little lacking though - I need to dig out the scan pics from my boys to see - this little lady has a very rounded head!
edgar I'd tell them too. I think work are legally not supposed to ask how long you are having off anyway, they have to assume you will take the year off until you tell them otherwise - and then even then you can change your mind (you have to give them notice I think). You have done amazingly well hiding it from them, I am so glad I told them at 12+4 so I could move into maternity trousers, breathe out and stop hiding my pooch!