As far as I am aware the only pensions which were awarded to men following WW1 service were disability pensions; if they survived the war and were physically fit then they were simply demobilised back into civilian life to cope as best they could. Widows were awarded a pension, as were other dependants, children and, in some cases, ailing parents. I don't think that any of the men who served in WW2 got pensions either. Of course, if and when those men reached the pensionable age of 65 then they would have qualified for the state pension, just as is the case now.
[Modified] I should add that men who were regulars and served their full time were, I think, given pensions. The whole process of demobilisation is very well described and explained here:
http://www.1914-1918.net/demobilisation.htmjds1949