Thank you JenB,
Appreciate your thoughts, you summed it up well in your reference to 'easily accessible information' - most if not all the information is available to me through sources other than Family Search and I am endeavouring to access those when I can.... Joseph's Will is such in point - and I am grateful for John in transcribing that - unfortunately it doesn't mention his alleged parents, but I will try to access the physical copy as with all other Victorian documents that have arisen so far at some stage.
Wholeheartedly agree, a subscription to FS would make it easier to access information but appreciate I have strong reservations on that company together with their business model and would certainly not offer false information in order to access their platform - I offer no judgement of what others may or may not do. Hope you can respect that and if I do post another query, will certainly mention I am not a subscriber to them
I am in the process of obtaining some of the BDM Discs for Northumberland as similarly those Durham Records in trying to narrow down the search criteria for William (and Mary) and any possible family in that area. It will be some weeks before I receive them.
It's looking like they may not have resided there as Joseph claimed in the material so far yet Sarah's parents appear to be accurately described
I have to prioritised the material I purchase to direct the search toward the original query and that was finding William and Mary - considering Mary Ann Kell Mason is (most probably) the daughter of Joseph and Sarah, doubtful information on her alleged grand parents would be shown on any of her certificates....so haven't sought them at this stage. I am slowly going over the material again that has already provided together with the many reference sources.... in more detail now given the additional information that has been uncovered..
I managed to obtain access to the Northumberland Wills Indexes 1858-1878 - the Blakey's are listed but on checking for the Mason's - no Williams at all....only Mason listed in Tynemouth - being Sarah Mason of Murton who died 25 Apr 1876. I will purchase that at some stage but am waiting on the discs to arrive..... it's a riddle within an enigma !

Thank you for your help....we have uncovered lots of information on this family, far more than I ever anticipated (anyone would have trouble believing it too) and it's all been done by generous contributors such as yourself and others who made it possible.......it truly is amazing and demonstrates the wonderful nature of those assisting
I'll keep working on it and if anything pops up I will post to this thread immediately, hopefully the material I ordered will open other avenues once I get into it but am confident we'll sort them out - think we've managed to knock a few bricks loose in the original brick wall I hit; given the shared interest so far......