His birth:

Surname   First name(s)      District   Vol  Page
Births Dec 1906   (>99%)
TOWNSEND George William    Cambridge 3b 419
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This birth is in Cambridgeshire so looks like theirs, the only plausible one:

Surname   First name(s)   Mother   District  Vol  Page
Births Jun 1933   (>99%)
TOWNSEND Maureen Cave Chesterton 3b 562
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In 1939 no clear entry could be found for him, though there is one for an Ida with a couple of redacted children.

There is also a birth of a Rodney Townsend in 1950 in Uxbridge but this is far more likely to be to the Townsend to Cave marriage in Brentford in 1945.
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A possible death in Cambridge with a believable birth date, but no related probate found:

First name(s) GEORGE WILLIAM
Last name TOWNSEND
Gender Male
Birth day 26
Birth month 9
Birth year 1906
Death quarter 3
Death year 1985
District Cambridge
Register number 985
County Cambridgeshire
Volume 9
Page 712
Country England
Record set England & Wales Deaths 1837-2007

Though there is a probate for a George William Ernest Townsend of a Rest Home in Acrington, Lancs but is unlikely to be his with the additional forename of Ernest and does not match the Cambridge death registration.
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Their marriage, the only George W Townsend to be married in Cambridgeshire:

Surname   First name(s)   Spouse   District  Vol  Page
Marriages Jun 1931   (>99%)
Cave Ida M Townsend Cambridge 3b 1228
Townsend George W Cave Cambridge 3b 1228

But Ida M Cave is not on FreeBMD’s birth recordds.  But there was one on Scotland’s People:

No Year Surname Forename Sex District City/    GROS
                                              County/MR  Data

1 1900 CAVE IDA MARJORIE F STIRLING  /STIRLING  490/00 0080

But this conflicts with (a) her age of 23 recorded at marriage in 1931, her birth date in 1907 in the 1939 Register and her birth date recorded on her death index.  So this Scots birth in 1900 must be abandoned.
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There are three Townsend-Cave marriages in England and Wales from 1930 to 1950, though the last is female-male so not right:

Last Name First Name Born Died Event Location
Townsend George W — — 1931 Cambridge, Cambridgeshire, England
Townsend Ronald — — 1945 Brentford, Middlesex, England
Townsend Audrey V — — 1947 Lewisham, London, England

The third of these would be the parents of the Rodney Townsend born in Uxbridge district in 1950.

So it looks like George and Ida had but the one child.  Though there are two redacted (ie child) entries in the 1939 Register.

Remarkably, now that I have done all the above her birth clearly appears on FindMyPast.  See her Person Sheet Notes, etc.
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Their marriage certificate adds the following:

Marriage Cert no 248 on 1 June 1931 at Christ Church in the parish of St Andrew the Less, Cambridge.

                His                       Hers
Names           George William Townsend   Ida Muriel Cave
Ages            24                        23
Status          Bachelor                  Spinster
Job             Factory Hand              -
Residence       24 Norfolk Road           29 Abbey Road (she was living there in 1911)
Father          John Albert Townsend      Charles Cave
Father job      Cycle Agent               University Laby

Witnesses       F H Drane (husband of his sister Emily), C E Cave (her father?)

Celebrant       John E H Lebanrood
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