I think this might be Kathleen...
GRO BMD references:1909 Q3 Birth - Kathleen Marion Day (mmn: Kidman); Huntingdon; 03b; 234
1938 Q4 Marriage - John G Baron & Kathleen M Day; Lincoln; 7a; 1396
1994 Q3 Death - Kathleen Marian Baron; born 26 Aug 1909 Blackpool & Fylde; district 5811B; reg B39C; entry 027; date 09/94
Likely looking deaths for the other siblings...
GRO references:1995 Q1 Death - Mabel Louisa Featherstone; born 18 Jan 1911; Newark; district 6881; reg 37A; entry 211; date 02/95
1998 Q4 Death - John Edward Day; born 05 Jul 1912; Newark; district 6881; reg 44A; entry 211; date 10/98
1999 Q3 Death - Leopold Henry Day; born 24 Feb 1908; North Lincolnshire; district 5441C; reg C42B; entry 255; date 09/99
2003 Q4 Death - Randolph Reginald Day; born 17 Nov 1914; Colchester; district 469C; reg C89C; entry 189; date 12/03
Other references:09 Feb 2009 Death - Charles Day; born 22 Jul 1917; Newark; postcode NG23 7
Possible probate for John Edward...
name: John Edward Day
died: 27 Oct 1998
probate: 23 Feb 1999, Manchester
probate no: 77009
type: Grant and will
http://www.rootschat.com/links/01mqz/