Hi again,
my full name is D.J.Moore.
The infomation I was using before came primarily from O'Hart's Irish Landed Gentry (1887). I checked up McLysaght's Irish Families, and he largely concurs with Hart, stating that Thomas De Jorse came to Ireland in 1283, married an O'Brien of Thomond, before going to Connemara whereby he became a liege of the O'Flahertys (The family later became independent of their overlords). MacLysaght also notes that the Joyces "were known for their exceptional stature". Joyes was the widely used medieval spelling of the name - William Joyes was Archbishop of Tuam in North Galway at the dawn of the sixteenth century. Shoye and Cunnagher are also apparently other variants of Joyce. The Joyes or Joyces were one of the 14 tribes of Galway and the medieval Joyes/Joyces of the city branch were significant powerbrokers there.
Given the location, it's almost certain any family called Joyce of Joyes in Galway can draw their ultimate origin from either the city or connemara Joyces.