So, Harry joined Kingsman in or before 1981, because the newspaper cover from his first mission was a royal wedding picture of princess Diana and prince Charles. If we’re going by Colin Firth’s age, it means Harry was still 20 for his first mission.
Harry seems to be one of those quietly liberal people. His little “Catholic whore” speech in the church was before Valentine turned on the chips, meaning what Harry said came from his own self. People usually mellow with age, so when Harry was younger, he was most likely a more vocal liberal.
Basically what I’m saying is that my headcanon for young Harry is that he was liberal hippie trash that was constantly giving the other agents heart attacks with how reckless and boisterous he was.