Temprature guage keeps remains in middle in traffic. On motorways it goes down at quarter? Is it fine of the thermostat os stuck, i am getting 39 mpg , 1.2 panda 2004 , 72 k miles driven

I'd day you need a new thermostat
The temp gauge should never drop below 1/2 not unless driving in extremely cold weather e.g -6 and below

Almost certainly the thermostat. Not an expensive or difficult job.

Spike

It’s the thermostat.