Hijet 1.2Diesel - N Reg: Overheating


I have a Hijet Diesel that seemed in relatively good condition. It now overheats as soon as I idle. Any time I idle for a few minutes the temp guage rises and rises and rises...... ???

The radiator is only getting mildly warm and the oil and water arent losing any significant amount (in fact I have never had to top them up yet!) The fan isnt cutting in but I don't know if this is the problem. Could it be:

1) The thermostat? If so where is it located and how much to replace?
2) The fan? I have checked the fuse, its OK. What else could it be?
3) The radiator? If so, what could be wrong with my radiator?

I assume must be one of the above but dont know how to fix them. How do I get to the thermostat?

No circulation.

You have poor circulation so its either.
1. Broken/loose belt which drives the water pump.
2. Broken/stuck/rusted water pump. [No method of checking until its removed]
3. Thermostat stuck shut. Cheap to replace and diy.[most likely to be the problem]
4. If vehicle is 5years+ the radiator needs flushing out ... empty and hose throught the system. Use correct additive when filling.
5. Air blockage in the system.
6. Radiator cap not fitting secure so system is not pressurised.