Sadly I do not live in the UK which does make it an issue when I would like to go to various archive offices in person. I always used to do my own digging when I lived in UK - something I really enjoy and miss not being able to do!I have used LDS Family History Centres in Canada, England and now Scotland. I am extremely grateful to the LDS for their generosity in sharing the films/scans of original records with people like me who are not church members. Wherever you are there is a chance that there is a centre local to you, its free of charge and I find the people to be very friendly and helpful when I visit.
https://familysearch.org/locations/ that link will tell if there one you can get to.
and this link
http://www.rootschat.com/links/01kfi/ shows their holdings for St Joseph's, RC, Gateshead. Any item with a camera icon means they have digitised the records, 'sometimes' you can see them from any computer and sometimes you get a message saying they are only available to view at a Centre - but that is free. If its a film roll icon, then is possible to order the film in to any centre (though there will be a small charge for that)
I have a fair few records from St Joseph's and just looked at some which are slightly later than the 1884 baptism we are talking about but there are a good few amongst them that have been annotated when the child grew up and married.
Do you think my best option would be to get hold of the 1909 marriage cert for Mary Ann Green and William Gilliead rather than either of the birth certs for her?Do you know for sure that her Dad was James Green? I try to document the steps backwards, verifying at each stage that I am on the right track, especially for the direct line. If you don't have any evidence of who her father was then a marriage cert, as it 'may' have been at a Register Office, is probably the only way to find out. From there you can try the marriage records, census returns, etc, to try to find the family and track backwards.
You could try contacting the owner of the tree you looked at to see if they have any clues. Some trees on ancestry are reliable, some aren't. I look at them now and then and my usual rule of thumb is that I look at the number of people in the tree, if it runs into the 1000s then I gently close the page.
If I live a hundred lifetimes, I won't have the time to research that amount of people in any sort of accurate detail. I don't mean to disparage anyone, we each do our own thing, but I really am wary of the validity of very large trees :-)
Boo