If it is overheating when standing, but not when driving, the problem will lie with the cooling fan.
recently the missus car was runnin hot so i took it to a ex rover dealer. they changed the water pump and bled the system. tonite we decided to leave my r420 at home and take her car for a drive. while parked at a stoplight i noticed that the temp was rising waay above normal. so i stopped at a gas station to inspect for coolant loss but the coolant is fine . the heater blows hot air. but i did see that the radiator is in pretty bad shape and the cooling fan doesn't seem to turn very fast. i think my problem could be one of these 3.
1 bad radiator
2 bad cooling fan
3 faulty thermostat
plzz help me here as i would like to get the car sorted asap