How do you adjust .

brake imbalance! Out of interest. There is a thread on here about failing WOF's due to brake imbalance. I'm reasonably familiar with older style brake setups i.e. disc front and drum rear. The only adjustment I was aware of was the rear drums using a screw driver on the ratchet wheel. I see most cars are 4 wheel disc now . how are they done! And there was mention in that thread about some outfit using a machine to adjust them. Hows that work! Or did it mean the machine measured the imbalance! I've seen some meter thingy the mechanic placed in the passengers footwell. Is that the old school version of a brake balance tester machine then! Tell.

usually leaking cilinder or faulty brake proportion valve both caused by lack of service fluid changes. 24 month is the fluid change interval

Do you mean front:rear balance - or left:right!
Next time you go for a WOF at a testing station, ask if it's okay to watch when they test left:right balance.
If you've failed a WOF because brake balance is out, and you're doing a "DIY" to clean binding caliper sliders etc, you can't be sure that you've fixed the problem adequately until you get them retested.That only takes a couple of minutes.
With 4 wheel disks, if the L:R balance is out, there's nothing to "adjust",the LH rear is usually the first one to bind up, because the left side goes through more puddles and crap on average than the right, the rear disks don't get as hot as the front so stay wet for longer when you do go through a puddle, and as the pads last longer than the front they don't get periodic maintenance as often - as the pads aren't usually being changed very often (ie for one of my vehicles with 4 wheel disks, I changed the original set of rear pads only after it had done 200,000km / 20 years).But I'd had to completely strip and clean the calipers in the meantime.

the brake tester thingy is a tapley meter which measures overall performance of brakes,not individual wheels.New wof changes may see powers that be trying to get all wof issuers putting in brake rollers,which could be interesting for a lot of us.

You can still fail for brake balance, most experienced mechanics can pick it in a road test with or without a meter