Ubuntu – ny way to stop a window’s title bar merging with the panel when maximised

I'm working on a desktop machine with plenty of screen real-estate, so I don't need my windows' title bars to merge with the global menu bar when the windows are maximised. Moreover, I'm working on a dual-screen set-up, so the fact that a window is maximised doesn't mean that it's the only window visible.

Before Unity I'd switch to a maximised window by clicking on its title bar, or close the window, even though it isn't focused, by clicking on its close button; I can no longer do this because the title bar is missing and the global menu bar is empty on that screen. This isn't a huge problem – I can click on some of the window's chrome to focus it – but it's unintuitive and it's forcing me to relearn my mousing behaviour.

I'd like to turn-off the merging of title and global menu bars, but how?

EDIT:

I simply want the title bar of the window NOT to merge with the top panel whenever I maximize a Window. The global menu should stay in the top panel as far as I am concerned. Current it maximizes like this

I want it to maximize like this (In that screeny the unmaximized Window has been resized to take rest of the space)