Having had a look through keyboard shortcuts I couldn't see a key to clear the camera from the last selection.
Navigation in the render window is a right royal pain in that backside and would be nice to be able to clear the camera so it isn't rotating around the previous object (even if that object has been deleted!). Is this possible?

Click something else? You can always pan around by holding the spacebar or middle mouse button.

Pressing "d" will clear any selection.

He means if you've maybe selecting a few different objects, move them somewhere, the camera still pans the old location. Ok for a single object, because you can just reselect it. Annoying if you've selected lots.

You'll get used to this. It's actually better than how the camera used to work in previous editors. I'm to the point where I can navigate the render window effortlessly, far more effectively then I could with the GECK. It just makes some getting used to.