The only Dawn H Nicholson birth on FindMyPast from 1945 (making her 42 at the birth of her third son) to 1965 (making her 27 at marriage to the then 47 year old Derrick) is:

First name(s)         Dawn H
Last name             Nicholson
Birth quarter         2
Birth year            1963
Mother's maiden name  Chambers
District              Newcastle upon Tyne
County                Northumberland
Country               England
Volume                1B
Page                  290
Record set            England & Wales Births 1837-2006

So she would have been 29 at marriage.

I am entering this information as hers with the rider that it could do with some confirmation.  Possibly her marriage certificate would help with her age and her father’s name.
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The only marriage of a male Nicholson to a female Chambers is this between 1943 and 1963, and in fact a year before Dawns’s birth.

First name(s)       Ronald
Last name           Nicholson
Marriage quarter    4
Marriage year       1962
MarriageFinder      Ronald Nicholson married one of these people
                    Maureen Chambers
Spouse's last name  Chambers
District            Cleveland
County              Yorkshire
Country             England
Volume              1B
Page number         1115
Record set          England & Wales Marriages 1837-2005

There are two marriages in the same period between female Nicholsons and male Chambers in all of England and Wales.

So there is a strong possibility that Ronald Nicholson and Maureen Chambers are her arents.
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Their marriage index:

First name(s)       Derrick
Last name           Armer
Marriage quarter    4
Marriage year       1992
Registration month  11
MarriageFinder™     Derrick Armer married one of these people
                    Dawn H Nicholson
Spouse's last name  Nicholson
District            Bristol
County              Gloucestershire
Country             England
Volume              22
Page number         404
Record set          England & Wales Marriages 1837-2005
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