I have a 1993 440 1.7si. Not long back I had a water leak. It was established that this was coming from the water pump. So a new one was fitted. Since then my car overheats when idle. Everything in the Haynes manual has been checked also anything found on the net. The radiator has been checked. So has the thermostat. It has been checked for air locks. And has also been drained down and refilled with 50% coolant 50% water. Strangely it never once overheated with the water leak.

it will run hotter than before as you were losing pressure, check to see the radiator fan is coming on when you idle, they will normally run a little hot at idle if the fan doesnt cut in, one way of telling is after you stop with a warm engine the fan will run for about 30 seconds or so, to cool everything down, if it doesnt it could well be the temperature switch for the fan (on the radiator itself I think).
Grendel

The fan works fine. Even waiting at traffic lights can make the temperature creep up.

How high does it get, mine running normally used to sit just above half way, and at lights would creep to about 3/4, if you can flushing the heater matrix can help, they have a tendancy to get a bit clogged, and by flushing through in both directions until the water runs clear, then the heater will work excellently all winter, I used to do mine every autumn ready for the colder weather (there is a post on these forums somewhere that I did about it) this allows the heater matrix to lose some of the heat out of the system (the matrix is hot all the time, and when you turn the heater on it diverts the air past it, so it does help the cooling system all year. other things to check, are - thermostat, make sure its clean and working properly.
Cooling system, make sure the whole of the radiator is getting hot, if not that may need flushing through, if there is sludge in the bottom it will reduce the cooling efficiency, in the 440 the cooling system lives on the edge and really needs to be totally 100% for proper efficient cooling, I have also experienced the running hot in heavy traffic, and only when the system was completely 100% did it reduce, it still crept up a little but not as far as 3/4 (maybe 5/8?) I think as long as you are under 3/4 thats about as good as you can expect, if the fans cutting in its at least trying to keep the engine cool.

Grendel