Imogen is nice, I have'nt heard many of them around.. I only know 1.

We really like Amelia but it is currently pretty hot well down here anyway, it is my auntys name and we like to use family names.

Annabelle go the longer spelling it looks prettier.

Eilish its too hard unless you change the spelling you will always be spelling it and no-one will know how to pronouce it.
I think you need 2 middle names if your DS has 2. There are plenty of pretty old fashioned short names that would go with what you have choosen, and how often do you use middle names? most people don't go around calling their children the whole name.

Goodluck !!! sounds like you are doing very well by yourself.