In answer to Tigertiger, there are two types of fittings, the one the thread is about where the batten is similar to those seen in a kitchen or a premises where the tube is mounted in a batten, when it starts to flicker you either replace the tube or the little capacitor starter, there is the other type - a rubber flexible strip with multiple led's interconnected, both are good for saving electricity and yes the multiple strips are better for localised lighting because they illuminate close to the surface, the batten type are sometimes used to illuminate worktops by placing them under the wall cupboards and are usually about 200-300 mm long, we use the rubber flexible strip type for under ours attached to the pelmet.
I have two old batten types in the loft / workshop, a 4 ft (1200 mm) and a 5 ft (1500 mm), both are the old tube type the 4 ft one is a 36w T8, no idea what the other is, it's that old, so the general concensus at the moment is I could convert the tubes only or replace the whole units, I would prefer to just change the tubes and upcycle the fittings (the more ethical choice rather than throwing the fittings into the recycling stream). Discussion to continue?.