The soft spring comes into play when main stat is closed, you are at idle, and you move off idle to drive away from the light. The bypass disk moves to allow coolant to flow, but not force all of it thru the heater core. Makes temps stay more even also. But main thing is lower temps, so your 204 would be far less common. But your system is in much better shape than many.

 

They are not. I installed one. 195 degrees. I was sad.

 

This Disco is new to me. I have been a German car service manager for over twenty years. I could not understand why my vehicle would run so warm to hot. It's stupid. I understand why (emission) but this is a old engine. Everything is new in the cooling system, I do not want to get stuck, or my wife cooking the motor. I get parts at cost, so it did not hurt me to bad. Brand new German cars with electric water pumps run high temps thats fine, not a 40 year old engine. The soft spring thermostat starts putting water in the radiator even at idle. V8 flow is strong enough. To go from 200-220 at idle and cruise to 191-192 idle and 187-193 at cruise is nice. Heater cores are getting less stress also. And close loop in under 8 minutes or less. Fed gives 15 minutes. Only buy ome landrover thermostats, aftermarkets suck! With only air injection as the passive emission and no variable camshaft timing. Landrover and no choice but to run them hot.