Hello Debbie
Welcome to Rootschat!
The full entry for William Hart's Baptism at St. Hilda's is as follows;
8th March 1818, William son of William and Ann Hart, South Shields,
(father's occupation) Labourer.
You can browse through a lot of the entries for St Hilda's via the 'searchlabs' site
http://www.rootschat.com/links/03oa/ which contains a lot of the Durham Diocesan Bishops Transcripts. To save you time, this entry can be found on Durham/South Shields 1816 - 1825, page 38. If you work backwards from this you might perhaps come upon the marriage.
Have you got William and Isabella's 1845 marriage certificate - presumably his father's name was William?
I see you have put a very similar request to this one on the Durham board so to save possible duplication of look-ups I will put a link on that request to this one.
Hope this is of some help.
Jennifer