Mine just has the main thermostat - couldn’t find an inline one, and yes had an outlet temp sensor instead. it’s an 07 manual ed30.
I swapped mine out last week (eventually) and it is fine now - always stays between 84-87C.
Was pretty difficult job though as a lot of people have said! In the end I had the whole front of the car off as I also changed the intercooler, so it wasnt too hard but Id imagine its really difficult if you are just removing the alternator as there wouldn’t be much space to work.
I had to remove the black plastic boost tube up to the inlet manifold (sorry - doing know proper name!) so that I could undo the bolt holding on the black metal coolant tube which comes out the middle of the thermostat. I also really struggled to get the connector off the bottom of the old thermostat as had sealed itself on there pretty well. Would have been real tricky without having the access I had. Respect for those who have done it without taking the bumper etc off!