Yip, had one of these... common issues:
- Blockages in the radiators(I had to replace my Polo's radiator once, cause it cracked)
- Broken impeller on the water pump, also common at about 165000 Km
- Stuck thermostat
One of the easiest tests is, as the engine heats up feel the temp of the inlet pipe from the block to radiator(usually top one), it should heat up quite quickly, then as the engine get to normal temp the bottom rad outlet should also start getting warm, by the time the elec fan kicks in the top and bottom pipe should be about the same temp, then as the fans runs the top pipe should stay hot and to bottom pipe should cool down a bit. Make sure you have no loose clothing on when doing this check, else it and your head could get snagged
If the top and bottom pipe do not heat up(even after the temp needle has reach full operating temp), then I would suspect the pump; if only the top pipe heats up, even after the fan has kicked in, then the thermostat may be stuck closed; if, once the fan has come on for the first time(top and bottom pipes are hot), the fan stays on long 1-2 minutes(ambient temp 27deg or so), and only cuts out for short intervals, 30 seconds, then I would suspect dirty blocking channels in the radiator.
I remember my VW mech friend telling me the VW engines do not like any other coolant but the red one marked G12, I would also check with your nanny whether it has been topped up with coolant or water, if water only over a long time then the coolant will get diluted to the point where it is no longer adequate to keep the boiling point high.
Hope this chunk of data helps!
B
:? 
, finally I feel like I'm getting somewhere, this problem has had me scratching my head nê 
