Windows 8.1 is only a few pounds more expensive, and it will be longer supported.
http://windows.microsoft.com/en-us/windows/lifecycle
Windows 7 already has not support for the latest DirectX. That doesn't matter right now but i think it will be more important in the future. For some reason games tend to run better on windows 8 as well, although the interface is ofcourse not so great. I would personalyl go with windows 8 though, it's not that bad as people say it.
And yeah you should definitely get an SSD.. it's way faster than traditional hard drives and you will notice it really good. The system boots up faster and programs will load much faster etc.
And an optical drive only seems to be necessary for installing windows, if you don't have one from a previous pc you should buy one because windows comes with an DVD. I'm pretty sure though that you can install windows 8 from an usb drive, but i don't know exactly.