There were 2 births for someone with the name you are referring to, groom - one born Sept.1946 with maiden name Milroy in Wandsworth but another with same birth name born Dec.1945 Islington (different mother). The marriage in Islington probably relates to the child born there 1945.
I note that the man whom Margaret married was named Carl C. Colson - wondering if he was the Carl Clayton Colson born 15/6/1919 Florida who died and buried 1/11/1962 Arlington Cemetery, VA. I note from FindaGrave that his wife buried with him (she died 25/12/1999 and interred with him 10/7/2000. She is shown as Marga H. Colson - could this be some corruption of her name? Her birthdate is given as 19/4/1923 and can't help wondering if this is the birthdate of the Margaret Handli. Milroy born 1923 Maybole, Scotland.
Annette