the names looks much better now. I write here some more names, use them if you like them  
 
 your names:::                                      new ones:::                                     why
--------------                                         -----------                                      -----
cork:::                                                   munster:::                                     cork was established by Vikings much later
munster:::                                              leinster:::                                       leinster is more in this area as munster
limerick:::                                               dal cais:::                                        limerick was founded by Vikings.
leinster:::                                                mide:::                                           old kingdom
border country:::                                     oriel:::                                             old kingdom
ulster:::                                                  ulaid:::                                           old name
highlands:::                                            cait:::                                              old pictish kingdom
aberdeen:::                                            circinn:::                                          old pictish kingdom
garmpain:::                                           fortriu:::                                           old pictish kingdom
strathclyde:::                                          ystrad clud:::                                     older name
edinburgh:::                                           gododdin:::                                       old brithonic kingdom
cardiff:::                                                gwent:::                                          cardiff is town, gwent is region“s name
isle of man:::                                         mann:::                                             old form of name
the rest looks good. here is only question if you will use english form or also celtic. I“m not sure about London - it was not so important at this era, maybe better could be have it also as celtic sea - London it is just crossing point...?