I'm kinda in the same boat [but in the US].

I recently picked up a 96 4.3 and I am figuring things out as I go. My 4wHi light came on OK but I was still spinning in the rear. 4wLo just blinked and flickered. A mechanic friend suggested I buy a front axle "actuator" because it was the cheapest fix. the gal at the parts house said it was just a sensor on the cable housing but I bought it anyway. a "cheap truck challenge" video suggested trying to spin tires to determine if the rear end was open or limited slip [same test for front dif. as well.]

On the way home from errands i pulled off to a stretch of hard packed weeds with a lot of loose gravel in it for the test. For this "DRIVE" was not delivering visible tracks so I put the shifter in"L" and nailed the pedal each way. 2Hi spun at least one rear. 4Hi spun both a right and left together but I can't tell if it was on the front or rear from tracks. 4Lo really dug some parallel tracks !

I'm still unsure about the 4wd tests and willing now to ask a friend to watch for better verification but right now I have a severe coolant leak coming from behind the lower hose and the slight engine tap is now louder than the exhaust. I may have to adjust my priorities.