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 regionĀ“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. IĀ“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...?