the_constructor formulated the question :
How many lamps should I use, lamp fittings, cable etc etc etc.

I will be using the garage to do repairs to my own vehicles and other small
repair jobs but need good light.

You are not going to get good light from a 12v battery, at least not
for long. Probably best would be a few 12v florescents as used in
caravans, for general lighting, with a 12v LED light for more local use
in the area you are working on.

Best not to expect the car's own battery to supply the current - use a
leisure type battery which is designed to be regularly discharged. You
would need to take that in the house to charge it, unless you could
arrange a solar or wind charger.

In the dim and distant past and in similar circumstances, I used a
couple of paraffin pressure lamps to provide light (and some heat), but
not a good idea when messing near petrol.



--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk