With a heavy focus on romance, the series has many kiss scenes, usually quick ones between married couples.
As well as other minor references.
Wayne calls Kevin "Scrote".
In season 5 episode 1 Paul mentions a condom. Incorrect description of this information.
Sex, orgies, masturbation, boys looking at naked women in books, boys seeing naked women through windows, all of this is implied or talked about. Pretty much the stereotype of boys hitting puberty in the 60's.