Celtic Christianity was a form of Christianty that existed in Scotland, Northern England, and Ireland in the early centuries. St Patrick and St Cuthbert were proponents of Celtic Christianity.
The term “Celtic Christianity” is a misnomer because it implies that this Church was seperate from Catholicism; it wasn’t, they were entirely Catholic in their beliefs. However, they had different liturgical expressions and a different calendar. The structure of the Church was also different from the main structure of the Latin Church. Most of these differences were abolished through various Church councils and the Celtic Christians adopted the Roman practices.
The idea of a Celtic Church is essentially a myth because these Christians were united with Rome. During the Protestant reformation, many claimed that there was a Celtic Church that differed from the Roman Church; this is false.
This “Celtic Catholic” is probably a Protestant who is trying to revive some of the celtic traditions and spirituality. He will probably not be a faithful Catholic.