Common tbh small engine in a big engine bay it's never really get to hot. But yes i would try a new thermostat first tbh. Mine only really get to 85c ish when sat in trafic ect.

Probably a faulty thermostat. You can take it out and put it in a bowl of hot water and see if it opens at the correct temp if you have a thermometer to measure the water temp. Or if you cba, just replace it and see if it makes a difference.

had the car about a week now (vectra b 1.8 2002) and while running around enginne temp has never risen above 75 degrees, barely even lifts off the stop. is this something i should look into or normal for these cars, as my corsa always ran at 90ish assumed that was the right temp for most engines.