Revised Edition. 27/08/08.

Step 1: Turn your heater to hot.
Step 2: Remove the radiator cap.
Step 3: Remove the bottom radiator house. Becareful as it will come out quick. You will probably get coolant all over you.
Step 4: Remove the thermostat housing and the thermostat. The housing is secured with 2 bolts on the bottom of the engine. The bottom hose was connected to the housing. More coolant will come out when you pull out the thermostat.
Step 5: Remove the top radiator hose.
Step 6: Jam a hose (or use distilled water depending on how pedantic you are) into the top outlet of the radiator, run the hose until the water is clear at the bottom.
Step 7: Next put the hose into the top coolant hose on the engine. Run the water until its coming out clear on the thermostat housing.
Step 8: Remove your overflow bottle and give it a clean and then replace it.
Step 9: Refit the thermostat (inspect the condition of the seals and what not to make sure its hunky dory) and bolt the housing back on.
Step 10: Reconnect the bottom hose (inspect the condition of the hose to prevent heartaches).
Step 11: Get a funnel and hose and lead the hose into the top radiator outlet. Pour coolant in until you think its full (coolant starts coming out). (This is a step i threw in myself, it seemed like a good idea at the time).
Step 12: Reconnect the top hose (inspect the condition of the hose).
Step 13: Make sure the car is jacked up at the front (this helps prevent air getting locked into the system). Fill up coolant via header tank.
Step 14: When it seems that it wont take any more, start the engine. Watch the header tank for bubbles (small ones) and listen for gurgling (from the header tank). Switch off before it gets so hot that the coolant will start rushing out.
Step 15: Wack on the radiator cap.
Step 16: Monitor your temp gauge over the next few days to ensure that you haven't messed anything up.

Capacity wise, my car took 7ish litres. It was the same amount as what the workshop manual said. I believe the fact that I had to leave the car over night to drain (because my thermostat was damaged and i couldnt get a replacement) was the main reason why it took all the coolant. The last time i did it, it took closer to 5L.