Hi
If the son (ie: the husband of the still-living grandmother of your D-I-L) is the gentleman who passed away in 2003, with a recorded dob 25 Aug 1922, registered in Leicester - his birth could have been registered Sep Qtr or maybe the Dec Qtr of 1922 (if the dob is correct, that is!). That would fit with the Birth found under BATES in 1922, The mms for that birth is FORDER.
http://www.freebmd.org.uk/cgi/search.plNot seeing any BIRTHS for FINLOW mms BATES either, post the 1923 marriage or mms FORDER?
PROBATE: Kate FINLOW died 22 June 1960, widow of 34 Porter Street Leicester died at Hillcrest, 2 Swain Street, Leicester. Admin 11 Oct 1960, to Leonard BATES Plasterer, £4047, 4s, 5d
Her death was registered Leicester, Jun Qtr 1960 : Kate FINLOW age 80 (born abt 1880). If this is her then in 1923 on marrying FINLOW, she was age abt 37.
She may have been widow FINLOW for many years, if this is her husband:
DEATH, Thomas FINLOW age 49 years, Reg Jun Qtr 1928, Leicester.
Cheers
AMBLY