User blog comment:OneofthePendragon94/The age of Merlin, Arthur, Morgana and Gwen./@comment-5505930-20121114173130/@comment-5822565-20121114185157

as for surnames, here's a list of what i found to be the most common results:

merlin-Merlin Ambrosius

gwen- Gwen Degrance (next most common results were Smith or Thomas)

elyan-same as gwen, Elyan Degrance (Smith or Thomas) or sometimes known in the legends as Elyan le Blanc (elyan the white)

leon-couldn't find one anywhere

gwaine-Gwaine Lotson, in the legends he was Lot's son, so people say is surname was Lotsson or Lotson

percival-can't find one anywhere either

lancelot-Lancelot du Lac, or Lancelot of the lake, hence the title for series 4 episode 9 Lancelot du Lac

hope that helps!