Yes watched it last night.
Good bit of research there Blue 
Thanks. It started out as that can't be right it must just be the name being put down wrong but it happened enough to suggest that the name really was once McCarty or McCarthy and McCartney was a later variation that Paul's ancestors chose rather than the other ones. Some of the variations found:-
McCartey 1822 Baptism of James s of James & Ann McCartey (St Anthony RC)
McCartey 1841 Census of James s of James & Ann McCartey
McCarthy 1844 Marriage of James McCarthy & Rosanna Hughes (St Nicholas CE)
McCartney 1845 Baptism of James s of James & Rose McCartney (St Nicholas RC)
McCarty 1845 Birth registration of James s of James McCarty & Rose Hughes
McCartney 1847 Baptism of Anne d of James & Rose McCartney (St Mary RC)
McCarthy 1851 Census of Hughes family & Rose, James & Frances McCarthy
McCarthy 1859 Marriage of JA Templeton & Rose Ann McCarthy (St Anthony RC)
McCarthy 1861 Census of Templeton, Hughes & McCarthy
McCartney 1864 Marriage of James McCartney & Elizabeth Williams (St Peter CE)
McCartney 1866 Baptism of Joseph s of James & Elizabeth McCartney (St Anthony RC)
McCarney 1871 Census of James & Elizabeth McCarney with son Joseph
McCartney 1881 Census of Elizabeth McCartney (husband seaman) & family
McCartney 1891 Census of Elizabeth McCartney widow & family
McCartney 1896 Marriage of Joseph McCartney & Florence Clegg (Christ Church Kensington CE)
McCartney 1901 Census of Joseph & Florence McCartney & family
McCartney 1911 Census of Joseph & Florence McCartney & family
Blue