If it hasn't been said - welcome to the forum!
I'm fairly sure that water comes FROM the engine to the top of the radiator, so that's the hot side, and cools as it falls down the tubes in the radiator, and enters the motor at a lower temperature. Sounds like that part of it is working correctly.
We need to get back to some basic questions, one because I'm unfamiliar with that model. What kind of motor is it (petrol/diesel)? How good is the air cleaner? How long since the injectors/carby was serviced? How clean are the plugs? Does it smoke? If you start a warm (not hot) engine with the radiator cap OFF, do you see any bubbling in the water?
What's the rolling resistance like? Put the car on some level ground, drop it in neutral, let the handbrake loose and try pushing the car. Can you do it? Is it really, really hard to do or is it fairly smooth? You might have poor tyre pressures, or a dragging handbrake, and these things will cause the car to work a lot harder than it normally would.
