I'm the person mentioned by motherinferior as having changed ds' name after A YEAR (I'm glad you called me 'a very nice MNer', MI, not a ditzy cow who couldn't stand up to her MIL for a whole year )
I would try calling her Fleur for a couple of weeks and see how it feels. I did spend the first year of ds' life telling people I would really have liked to call him something else, and seeing how they responded, so in my terms you have all the time in the world. We went just over the year, so ds has two birth certificates - an initial one and an annotated one - but that hasn't been a problem so far.
I do like the name Fleur myself, and would have considered it for dd, except that a) I thought people wouldn't be able to spell it; and b) it's unfortunate that it rhymes with 'ugh' (pronounced errr) in English. So personally my ranking of the names you're considering, bearing in mind your surname, would be the same as Emily05's, namely:
- Megan
- Hannah
- Sophie
- Fleur
But I had peculiar, personal, gut-feel, mummy-type reasons for wanting ds to be called what he now is, and if you have them too, and as strongly as I had them, then I'd say go with them.