Harry Lot Ellis appears in a 1939 Kelly's directory in Worton Wilts as a shopkeeper and post office.
Many thanks Carol...maybe Harry is his birth name...the question now is whether he is indeed a Wiltshire boy born and bred, as I (have) always thought, or whether the marriage between Winifred and Harry in Q1 1916 mentioned by another kind soul below is indeed the right pair / marriage, and Harry is a Scouser...
There was nothing to stop a "Wiltshire lad " marrying in Ormskirk! As you know Winifred had a connection with Liverpool, having given birth there, and the Ellis Jones marriage in 1916 is the only likely one to be found and that there was a person called Harry Lot Ellis of the correct age alive at the time, I think the circumstantial evidence is quite strong that this marriage is the correct couple. Possibly Winifred went away to have the baby in 1913 and didn't reappear in Wiltshire until she was respectably married 3 or more years later.
In any case, Maxwell doesn't seem to have been Harry Lot Ellis's son since he is not named on Maxwell's birth cert, so the only chance you have to follow your patrilineal line further is to find out more about Winifred, which you can only do with certainty by ordering her wedding cert. As it looks like the wedding was in a Registry Office, buying the cert is the only way to check her age and father's name and occupation.