Hi Michelle,
From what you said it seemed to imply that Harry Williams was born either in Montgomeryshire or Shropshire.
I have found a Gerard Cowell Williams in the second quarter of 1906. the birth was registered in the Atcham District, volume 6a, Page 657. Atcham is mainly in Shropshire, to the west and north of Shrewsbury, and partly in Montgomeryshire. The reference was obtained from freeBMB at
http://www.freebmd.rootsweb.com/ If you have not used them before, it is a FREE
lookup site for births, marriages and deaths from 1837. By using the reference you may obtain a Birth Certificate from the General Register Office (GRO) at
http://www.gro.gov.uk/gro/content/ this will show place of birth, parents etc
The Marriage of Harry Williams and Constance Maria Oakley was in the 1st quarter of 1893 in Paddington District, volume 1a, page 21.
If you wish a Marriage Certificate may be obtained as above. This will show father's names etc
In the 1881 census for Oswestry, near to Atcham District there is an entry for a Harry Williams, born about 1867 in Oswestry, his parents were Jacob and Mary Williams, brothers and sisters Edward, George W, Thomas, Elizabeth, Margaret J. If this family sounds familiar I can let you have fuller details.
I loved your country when I visited. I was there many times, in Aukland and Christchurch, many years ago, and found the folk extremely pleasant and generous. Best of luck in your search for the Williams clan.
Cheers Dave