In viewing the Household Return form tor the 1901 Irish Census for James Spenser, it indicates Mary Spenser was born in Dublin City (I think.) It's a bit hard to make out the handwriting but I think that's what it says. If so, this is not my Mary.
I do have census records in England for 1861 through and including 1911.
1861 James Spencer is living in Southwold, Suffolk, England - his birthplace. Same for 1871.
Sometime in the 1870's he was a private in the Royal Horse Battalion in Dublin South
1875 he married Mary Archbold, possible and most likely "my" Mary
1881 he was living in Lancashire (Liverpool) England married to Mary Spencer, occupation bricklayer
1891 he was living in Kingston upon Hull, Sculcoates, Yorkshire, England as a general laborer Census inddicates May was born in Ireland.
1901 he was a dock laborer living in Sculcoates, married to Mary Spencer
1911 listed as a "former dock laborer" he was an inmate in the Sculcoates Union Workhouse - no mention of Mary, yet James' status is listed as married not widower. I find this confusing but I've seen it before where the husband goes to a workhouse and the wife is still alive. Not sure how common this is.
James' possible death record - December 1926 buried in St Peter's Churchyard, Rylstone, Craven District, North Yorkshire, England. Wife listed as Mary Spencer. This cemetery is an Anglican cemetery (as opposed to Roman Catholic) so not sure if this is the right burial place, despite everything else fitting.
I believe this is the James Spence(r) that married Mary Archbold in Dublin in 1875. He was originally from England, she from Ireland. More research to do to be more certain, but I think I might be in the right track.
Re: the Maguire connection, I found the Spencer family in the 1901 Irish Census. Looking at the actual record, it seems that all were born in Dublin City, including Mary Spencer. I then found Margaret Maguire in the 1911 Irish Census and looked at the other family members living at the residence: husband Loius, daughter Mary, mother-in-law and widow Mary Anne Spencer, sister-in-law Jane Spencer (Margaret's sister). This Mary Anne Spencer appears to be Mary Anne Molloy, I found her marriage record to Robert Archbold in Dublin City - so the Dublin City connection holds for this family. I also found her marriage record to James Spencer in 1884 Dublin. The actual record reads Mary Anne Archbold nee Molloy, a widow. I think I can rule out this family.
Best
Terri D