Lighting used to account for 9% of the average energy bill. Now with LED's this has gone down to more like 3%. This is good news! But there are still some important things to consider when choosing lights.
Ideally we don't want to need any lighting during the day. A reasonably sized window should accomplish that, or where the room or corridor is land locked on the interior of the house, a product like Solatube, or a Roof window, can bring light in. Paint can also make a huge difference. Consider lighter colours in the darker southern rooms, to maximise the light they get.
Be aware also that light bulbs are still in transition and while there are heaps of LED lamps these days, just check that the bulbs are in fact LED before you buy the fixture.
Lastly, try and avoid downlights! Firstly they ruin your ceiling insulation, introducing thermal bridges. (See Insulation). Secondly they require you to cut holes (usually multiple) in the ceiling plaster, increasing unwanted air infiltration, and making it very difficult to achieve a 'tight' building fabric. Today there are lots of downlights that sits proud of the ceiling and do not require large holes to but cut out. Or better yet, choose lights that hang into the room space as these generally make the most out of the globe's light.