While I've adapted to most things in Windows 8 quite easily, I miss the 'combined' search feature of Windows 7 where pressing Win then typing would bring up all of the applications, settings and files (not that I ever really used the files part). Now, if I want to search settings I press Win, start typing, then have to press the down arrow twice, then enter, then find the setting I want (I know I could press Win-w, but that's just another thing to remember). Is there any way to bring back the 'unified search'?
No. They dropped the unified search as we know it in favor of the new platform. This was largely done to accommodate the ability to search among a large number of apps that use this feature.
Since this is done by sending a Function variable into the app, which it handles according to its own programming, Microsoft has to set up their inter-OS search the same way.
They combated this issue with the new Win+W combination.
There's a simpler way than that but this answer won't answer your last question. It'll just make searching for settings quicker and easier.
Or you could get the Windows start menu back by using Start8.
It will give you same search function as the start menu from Windows 7.