Whom ever is considering inside vehicle LED retro-fitting,
China Town,Ottery, has a vendor of very affordable conversion applications (even if the festoon fittings are a little too long - the car's globe's clips can be bent back wider to accommodate, with a stretch).
!! NB -Just make sure lights are checked / working, before you leave the vendor's shop.!! 
It comes as a rectangular/square block, buy to fit size correctly, with multiple LEDs on the block, off which, there runs the two power cables, to festoon-like "plug". The light is far superior to the original 5-8w, and now consumes a messily .75-1.5w MAX.
A huge difference to one's power consumption, so much so, that when camping, I've often left on for the remainder of the evening, until retiring to sleep. They lights are also at the optimum positions and can be manually switched off, with the car's lamp switch.
As I have a drawer system, I've subsequently fitted an aluminum strip light above where the drawers / fridge opens. The aluminum strip lights, with long extension leads are great to hang in the tent / rooftop tent (which I have), side awnings, or just to suspend in a tree, near to the braai area.
All these applications can be directly of indirectly used off an auxiliary battery pack, and, even with the fridge working of the same battery, the consumption is kept to a minimum. There are now even flood / spot lights available, to use if a huge amount of recreational / work area light, is required.
I'll post some pics in second half of June, when I return from my overseas trip.
Regards
Achille
