Matiz facts continued...
- Yes, I do think it is a good idea to change the cam belt at 30000 miles rather than 60000 miles. However, I am not aware of cambelts breaking before the recommended period.
It is good workshop practice to replace the tensioner when replacing the cambelt but not essential (unless it's noisy or feels "rough" when turned by hand).  It is possible to change the belt in situ, removing the RH headlamp helps with room.

-The right hand wheel arch liner does have to be removed to gain access to the washer bottle assembly.  Just a quick question: does the rear wash wipe work?  Fuse No 9 in the internal fuse box protects the rear wash wipe function AND the front wash only. Is the fuse OK?
You are right about the workshop manual, there is no Haynes manual. You can buy the Daewoo Matiz manuals from GM Daewoo (but they are not cheap).

-Change your engine oil every 12 months or 15000 Km.
If you live in a dusty area, every 6 months or 7500Km.
Make sure you choose a good quality engine oil.  (SAE 10W40)

-You may need to purchase an oil filter wrench to unscrew to old filter if it has been overtightened.  To get more access to the filter: 1.   remove the air filter/resonator assembly.
          2.   remove the heat shield.
          3.   loosen the power steering pump hose bolt and pull the
                hose forwards out of the way.
This should give you more room to get to the filter.
When you refit the new filter, remember to lubricate the rubber seal with clean engine oil.  Do not over tighten.

-How can I refresh the GEAR BOX Lubricant?
There is a drain plug on the bottom of the gearbox.  After warming up the oil in the gearbox (take the car for a short drive), remove the drain plug and let the old oil drain out into a drip tray/ container.  Replace the drain plug and tighten.  There is a filler/level plug (located next to where the LH driveshaft comes out of the gearbox).  Remove the filler plug and pour in the fresh gearbox oil until it dribbles out of the filler hole (no more will go in).  Use SAE 75W-80 gearbox oil or equivalent.  Replace and tighten the filler plug.

-Hiccup on low revs
1. Between the throttle housing and the inlet manifold is a thin rubber gasket.  Is this gasket in good order and positioned correctly?
2. There is a stop screw on the throttle body which the throttle assembly rests against when your foot is OFF the pedal.  This screw is set at the factory and should not normally be moved. I would experiment with the position of this screw to see if this fixes the fault. First, I would set the screw so the throttle is slightly more open at rest. Make sure you make note of the original position just in case it does not work. Try half a turn at a time.