You are correct about the "0" in Fon and there should be a tor bach or circumflex above the letter O
Another one is Sir Fflint, should that be Sir Y Fflint? That's how the County Council refer to it. The strange thing is that the correct Welsh names for both Fflint and Rhyl are Y Fflint and Y Rhyl but the Y seems to have been dropped along the way
Now the other one I'm not sure about and can guess at why the word has been mutated but I am not sure if it is grammatically correct due to my lack of Welsh
Gymraeg a Saesneg shouldn't that be Cymraeg a Saesneg?