Overheating 1995 v8 disco

Hi Folk's I need some advice , I could see water dripping from the hole in the water pump I topped up the water.later on stopped at the lights in a cloud of steam the small hose that conects the heater pipe to the thermostat housing had split got home stopping every now and again to top up the rad . Fitted a new water pump and hose,took the car around the block checked no leaks thought great. Yesterday over heated again , doing about 70 uphill on the A120 got home stopping every now and again to let the engine cool, Thought it must be the head gasket.This morning took the car for a run to get it warm looked in the oil filler at the rockers expecting to see white foam nothing just a golden colour,removed the plugs they all look the same light brown carried out a compession test with the following results.
No 1 165 lbs in No 3 165 lbs in No 5 165 lbs in No 7 170
No 2 168 lbs in No 4 170 lbs in No 6 168 lb in No 8 170 lb in
No bubbles in the expansion tank ,drove the for about 5 miles temp normal.Any idea's why it overheated .

What's the condition of the rad like??

The only time mine got hot is when the rad was baked inside a case of mud / clay

Hi RobP rad looks ok put the hose on the fins water went throu, I have put some cleaner inside the system we use when power flushing central
heating. I wonder if its crap in the rad, it only overheats under heavy loads. I am going to take it for a run this morning then flush the rad.

I have just come across my old post so I though I would update it, I cleaned the rad out changed the waterpump and it took age's to get the air out of the system .But its all OK now the temp gauge sits in middle even in heavy traffic.