LEDs (striplights are cheap and plenty bright) + 12 volt battery ( maybe jumpleads onto the battery in your car?) - or - a handheld LED inspection light (get one with newer COB leds). I have a big Makita + sensible Sealy (07 on the list below, £25), both very good. www.designrhome.com/lamps/rechargeable-inspection-lamps.php Aldi / lidl do similar lamps about £5 but they use AA batteries not rechargeable.
3 lengths of that on a car battery makes it bright enough to work in there , still use a magnet torch for close up work , pretty impressive for almost no ££...also well worth doing the walls with some cheap white emulsion
if thats not cutting it or for long jobs , any chance to run an extension to it?
car batt charged in the house, LED lights (MR16 bulbs work great and you can just put choccy blocks on them instead of a holder) and get a car stereo wired up. and get a really good head torch (not one that takes triple As! THrow a used 250w solar panel on the roof and a charge controller and you are sorted for summer.
It's a block of 3 garages to the rear. Mines in the middle it's metres away but there's a neighbor's garden and a tarmac area. So no trench I'm afraid.
Could you run an extension cable overhead? That's how the power in my barn works with another long extension from there to the engineless bus body we use as an additional workroom/sleepout.
I do the same with my garage, it about 3 metres away from my so have a extension lead running over head and into the garage the plugged a light into it, works fine for me. Cost about £30 in all with a powerful light.
My old man does the same to one of his sheds and that's a good 8 metres away.