Thanks everyone (though you haven't really helped as I'm more convinced than ever that it has to be Esther! 
)
PoppyA - this is exactly how I imagine an Esther to be - it's a classic, lovely name, strong, not too girly. I can imagine a little toddler with the name (or nn Essie or Tess), but also a classy woman! There was an Esther at uni with me and she was stunning, cool, v. intelligent. I know a few grown up Esthers and they are all lovely. The problem for dp is that the only Esther he has ever heard of is Esther Rantzen!
Comtesse - I was reading a magazine in the hairdresser the other week and there was an article with Giles talking about how much he loved his wife [sick emoticon!]. Maybe I should google some pics of Esther Williams to show dp as well?!
Aargh!! You know when you have that one name in your head and no other will do? I've tried liking Bethany / Beth - it is a lovely name, but it's not the one for my dd. I agree that it's too girly, bland and uninspiring (no offence to any Bethanys out there!). I'm not keen on using Beth on its own (people will always wonder what it's short for). Maybe Bethan (though it sounds like Beth Anne to me), or if we're going for Biblical places, how about Bethlehem?! (though what if she marries a Mr Steel??! (although I do like the song! 
))
So, forgetting Esther and Bethany, it's probably going to be another old testament/Hebrew name (to go with other siblings - btw, we're not religious, it's just worked out that the names we seem to like are biblical, which irritates my mother no end!!).
I don't like the usual suspects of Rebecca, Hannah, Sarah, Leah, Naomi. I do like Martha, Marion/Miriam/Marianne (if not entirely convinced), but dp doesn't! I love Astrid - it has always been on my lists, but don't think we'd get away with it round here / it doesn't "go" with the others and dp hates it! 
. I do like Rachel, but I can't get past the fact that we know about 90 million Rachels of varying ages!
I just hate that we are both so stubborn on names and we are hoping that the other one cracks, and then we're going to end up with a compromise name that neither of us actually likes! How can I bully convince dp that Esther is the one?! (I'm joking btw - it wouldn't be fair to name the baby something he hates! I'm just sad that she won't be Esther . But equally, he has to come up with something other than Bethany - I've tried to like it but I just can't see it!) Maybe we will have to resort to the name my youngest picked - "Daisy Cookie"!!! 
Sorry, this ended up a bit long!