Not that I want to get into a fight[1] ;-) the Ferranti was sold in 02/1951, the UNIVAC I was sold 03/1951 and the Zuse Z4 was sold 09/1950.
Not sure the Colossus was a commercialy available computer everyone could buy in '44? The Z3 was "sold" in '43 to the GAC - but was not turing complete in '43.
[1] My personal believe is it's those geniuses not countries that did the invention, it's often a team effort, people are standing on the shoulders of giants and it's always difficult to define "first" plus at the same time irrelevant.