Try something like this:
https://www.screwfix.com/p/philips-g13-t8-led-tube-1600lm-16w-1200mm/7258v
I’ve got one in the kitchen and it’s been fine for the last 4 years since we had the room renovated. Obviously they dim over time but it still looks as bright to me (or maybe my eyes are ageing at the same rate as the tube).
The next version of the human rights convension is going to outlaw small domestic garages for car enthusiasts.
Sad thing is i used to put an Audi A4, BMW 5 series and an X type jag in the garage, and had more room width wise to get in or out.
Ah, I think you need to find a good electrician with a sympathetic ear.
The old usual (cheapest) fluorescent tube lights have a starter (little plastic plug-in canister about the size of a C cell battery) on the side of the long white box the fluorescent tube lives under, and inside the box a combination choke/transformer, and maybe a power factor correction capacitor (often just one shared between a pair of tubes on the same light switch). The starter is the thing you can hear clicking when the light is trying to strike and become bright, also goes wrong quite often. The choke works like an ignition coil to produce enough volts to trigger the current flow, and the transformer part of it powers the heaters at each end of the tube, but once the current flows in the light it is no longer much of a transformer and the heaters cool down.
The electronic ballast is a clever chunk of metal with wires on each end that lives inside the box. It replaces all of the fiddly unreliable hot gubbins that used to be in there, and always light the tube with no fuss and the tube heaters last forever.
You can make better use of the tubes by putting them lengthways in-line in the garage, two each side approximately three feet in from the side walls (if six footers) or three each side (if five footers). If you have the tube too close to a wall you lose half the light (wall too bright making the rest look dark). Add some individual spots for the workbench, to aim at pieces under scrutiny.
The insides of the tubes get dirty (with evaporated heater filament) as well as from the normal dust on the outsides, especially if they were in the old type of fitting which hammers them with the clicky starter. Hence my suggestion for new glass.
I could not see if yours have diffusers, but these are a cosmetic waste of light. At work we had many OCD types, one of whom wandered round with a light meter to prove a point, and all the labs had the lighting re-arranged. (Not me, they made me look almost normal.)
As said by others, you need to declutter and a nice bright floor paint instead of dark carpet would help reflect the light. I’ve also got four twin 5 ft tube sets and loads of light despite not having the ceiling covered/painted. My chum up the road fitted LED lights in his garage and as much as they are more economical, they just don’t seem to put out the same brightness as my tubes.
Try these.
My garage is the same size.
I have 3 on the roof, 4 around the walls. I wired the roof and walls separatly. I also wired them so they plug into the wall sockets so I can use either one or both. Avoids getting an electrician to wire them into the fuse box ect. I also have one on a 10ft lead to thow under the car and wow it makes a difference. The original lights are also still there.
I have one in the bedroom/workshop and it lights up the entire back garden.
Well worth it.
From what I can see there is just too much “Stuff”, hanging, wall mounted etc., which is absorbing, blocking, deflecting what light there is. As Drumtochty says your garage can either be a workshop or shed, it’s virtually impossible for it to be both. Mine’s 4.5m x 5.0m and it’s definitely a two-car shed!
while i have been on lockdown and forced holidays from work i have made some progress on decluttering , sorting , painting and lighting my garage / workshop.
Hi
Try turning the lights 90 degrees. Run two 1.8m spaced down the centre then. Repeat this down the sides, say about 1 ft away from the wall if possible. put new lamps in, use 38 mm style, not 26mm, as they will start better in cold weather, replace starters with electronic one.Have a task light over the bench.
To get max results paint the walls white and the floor a light colour.
If you had reflectors fitted above the tubes you would get lots more light from the fittings.
thanks for all the ideas guys , but all is in hand ( i hope ) 
i’m currently waiting for an electric paint sprayer arriving , 
I’ve fitted LED panels suspended from wires and just finished white washing the walls (had some spare time…). It’s really lovely and light. I’ve done some tidying since that photo.
A paint sprayer would have been a good idea I think, quicker than 2 coats with a 38mm brush!!!
Hi Robbie, I started with brush and gave it up as a bad job , straight on eBay and ordered sprayer 
How you finding the panel lights , I have these to fit ( once painted ) but mounting them flush to lowered ceiling/ hidden shelving. Mine are 4 x1 ft , 3400 lm per panel 
DAYLIGHT WHITE Led tubes all day long.
Transformed my garage.
You can get just the tubes or the whole fittings.
Got mine from eBay, various good companies/sellers on there.
I have a large single garage and used 3 sets of the attached:
I haven’t painted the walls white but they are very effective and can wax the car quite happily under these lights, I also have a scangrip Nova R cordless light on a stand which makes it even brighter And helps direct light around the sides of the car where it is darker
Oooo, you’ve done the roof trusses. That idea keeps crossing my mind…
Have you considered some insulation?
From what I can see it looks like most of the heat will be going out through the roof, then the drafts (and doors?) and finally the walls.
Also useful in summer.
Just remember to leave a breathing air space to the outside between the insulation and the tiles-underlining to prevent winter condensation.
I put some of the 1" FR5025 into my up and over garage door between its ribs, this made a big difference being the last uninsulated part of the building.
i have just finished my central lowered shelf , its 950mm wide , 3.6 m long and gives me 300mm depth of storage.
mounted underneath this are 3 x LED panels
i still have 2.2 m of head room which is great , i have to stand on steps to put things on to the shelving .
this will be used to hide deck chairs , loungers , etc. (longer things that i dont want on show , absorbing all the light .)
the joists also received another coat of paint ,
still more to do !!!
Ingenious storage and lighting solutions, the Ikea of garages. Nice work.
