Hi Emma
Welcome to Rootschat.
There is a marriage of a Thomas Galtress to a Gertrude Harrison on FreeBMD. The reference if you want to get the marriage certificate is
Dec.1914 Birkenhead 8a 1078 (Dec.means they married probably between 1.10.1914 and 31.12.1914.
Also on FreeBMD there are the following Galtress births, with the mother's maiden name Harrison:
Thomas - Dec.1916 Birkenhead 8a 867
William C Sep 1918 Birkenhead 8a 759
Margaret G Dec 1919 Birkenhead 7a 965
Doris Dec 1921 Birkenhead 8a 860
Frederick Sept 1923 Birkenhead 8a 851
If you start off by buying the wedding certificate of Thomas Galtress and Gertrude Harrison, you will find out their ages and the names of their fathers.
If you want to find the marriage details of Lawrence Williams and Doris Galtress, which I guess would have been in the late 1930s/early 1940s, you will need to trawl through marriage records on either Ancestry or Findmypast. You can buy credits for either of these, or possibly get free access to Ancestry from your library.
Hope this helps and starts you off on your new hobby

Lizzie