Where is the thermostat located on a 1997 Opel Astra 1.4?

You will find the thermostat in the t.stat housing bolted to the front of the cylinder head.Unfortunately like similar vauxhall engines,to get at it involves removing the cambelt and it's rear cover.I always recommend replacing the belt at the same time as the faulty thermostat if your mileage is getting anywhere near replacement time.This cuts down labour costs of course.