If your ancestor was definitely James RW Betteridge b 1908 - then he must be the one on the 1911
I have her father down as James Richard W Betteridge born in Grangetown, Middlesbrough 1908 he married Marie M Grimm in Cleveland 1938
There is such a marriage on freebmd and only one child was born to that marriage.
Marie Martha Betteridge (Grimm) was b 1898 and died 1976. As she was 40yrs old when she married James - that could be why they only had one child
I suspect Marie may possibly have been previously married as there is no birth reg for a Marie Martha Grimm