Sorry I did the maths wrong. Little one is 20 weeks (born mid Oct), and the new one is due within a week of her birthday, so on a recount I think I'm 8 weeks not 12.
Thank you so much for your inputs. I had to smile as I have a DS who would now be 13 (late MC) from a previous relationship and DP has 2 adult sons from a previous relationship. Our boys have 5 names between them and they've all been suggested. You lot have great taste in boys names haha!
I'm not too woried about Aubrey having been used for girls in the USA as I've got no connection with there. To me though it's very much an adult mans name, so I wont be considering it for a girl.
Of the suggestions so far the ones that are jumping out:
Talia/Thalia (silent H)
Coralie/Coraline
Aurora
Violet (but do not like Vi)
Lillian/Lilia
Romilly (no spelling preference yet)
Ivy
I also thought of Aurelia, what do we think of that?
Thalia was what we expected to call DD2 but she clearly wasn't a Thalia when she was born, so she ended up a Saffron, which more suited her bright sunny scampish nature.
Then for boys:
Sebastian is gorgeous, possibly enough to change my mind for, although DP hated it last time, but if he wont join in that's tough luck on him really. 
Because of initials, we can't have any names beginning with P. Otherwise Pearl would have been lovely.