I'm accumulating a file of alternative spellings for medieval names of interest to me. Perhaps you will find it helpful as well. I've optimized the format for Google Search.
There are several sources for the diversity, including:
Christian names from the same root are spelled differently in the common speech of different countries, and differently in Latin, and differently today.
Different languages use different spelling rules for the same sounds. The name of Verchin or Werchin from what is now northern France was recorded as Averxiu by Aragonese scribes.
Reliably consistent orthography was not a realistic goal in a society that could not produce dictionaries cheap enough for broad distribution.
Given Names and Nicknames
Clignet OR Clugnet (Blinky)
Colomat OR Collemach
Jean OR Jehan OR Johan OR Johannem
Pere OR Pierre
Tanguy OR Taneguy OR Tanneguy OR Tenneguy
Full and Surnames
Jean Werchin, Seneschal of Hainault
Werchin OR Verchin OR Averxiu
Carmen OR Carmin OR Carmenien OR Carneau OR Kerneau
Seneschal OR senechal OR senescal OR senescall OR senescallum
Hainault OR Hainaut OR Haynau OR Hynnault OR Henaud OR Henaude OR Henaut
Moncada OR Montcada OR Moncade
Santa Coloma OR Sante-Coulombe