I am a very light brake user, .....
Does that mean you 'brake' on the gearbox so the poor buggers behind have to guess when you're slowing down?

Like we were taught to 
Mind you, for me, the engine doesn't provide anywhere near enough braking 
Brake pads are cheaper than gearboxes..... We were taught (at advanced driving level) to use either the brake pedal or the clutch pedal singly i.e. either one or the other. You are either braking or changing gear, never both at the same time.
Do all your braking with the brakes to achieve the correct roadspeed desired then block change to the suitable gear to drive on with.
Still do, to a certain extent, with the autobox. Brake off the speed in a oner, then drive onwards as required rather than brakes on/off/on/off/on/off.....
Totally agree, for all vehicles with
modern brakes.
The "older" technique of engine braking was based on the fact that old drum brakes were highly inefficient at any speed, tended to overheat very rapidly when used at high speeds, and were, comparatively, expensive and time consuming to replace.
The technique mentioned of either brake or clutch, never both, is mandatory for all LGV/PSV driving ... breaking (

) that rule is an instant fail of the test. (Obviously for the pedants .. you do brake and clutch together as you come to a halt .. but under normal driving it is a no-no....

)