Cooling fan kicking in at 30 on gauge

[William greaves]

2011 1.4 turbo issue 

Run car for 8 mins the top hose is hot  Cooling fan kicks in but bottom hose is cold but I have a fantastic heater I have changed thermostat no air lock and no oil in water took up the road for but still bottom hose and rad is cold even after 15 mins

[Vauxhall Owners Club]

What temperature is displayed on the instrument panel?

generally, the thermo-syphon effect within the cooling system means that the top will be hot and bottom will be cold and the coolant circulates (with the assistance of a water pump) within the engine and ancillary items such as the heater.
Therefore the bottom hose should be a lot cooler than the top one.
If you measure with an infrared temperature gun, the temperature should fluctuate (without any sharp dips or peaks) throughout the engine.