2002 ka 1.3 duratec, overheat problems

Hi all, new to this site so bare with me, my wife has a 52 plate ka 1.3 duratec, having major problem with overheating, the engine gets hot in a matter of a couple of minutes, we have had the thermostat changed, its now removed, new water pump, new heater control valve, new bottle and cap and new radiator fitted, and still have the problem, no water in the oil, no oil in the water, no loss of power, ticks over as it should, it erupts like a volcano out the expansion bottle within 5 minutes of running, even put a bottle of steel seal in it to no avail, anyone come across this sort of thing before, baffled, any help would would be very welcome, thanks in advance