I'm not sure if our colonial friends use the term "old age pensioner" (do they even have pensions? A country that doesn't have a national health service would surely be content to leave old folk out to die in the wilderness once their economically productive days are over), so I decided this would be more appreciated here.
We mostly call then retired. Some here have pensions, others rely on Social Security retirement checks (cheques).
We all get pensions of varying amounts...depending on how long we paid the national insurance stamp. There is a minimum...which I would hate to have to be living on. Then we have our private or occupational pensions as well.