I learned this song and gestures in the early 60's, not sure if it was 1960-1961 while playing Rugby Union in Doncaster, or in 1962 - 63 with our Pothole Club when I went to University.
John Mehlberg's description of the gestures is pretty accurate. I would add that the two finger gesture was an enthusiastic up and down motion of the traditional English F... You, equivalent to the US single digit insult, possibly as an entreaty to the other team!
It is possible that the US personnel would not translate this gesture with the same background meaning.