I am looking for biographies of pre-twentieth century herbalists and
healers from the Celtic countries (Ireland, Scotland, Wales, Isle of
Man, Cornwall and Brittany). The list should go as far back in time as
possible.

I already have plenty of information on ninteenth century healers from
Ireland such as Biddy Early, Mac Govern, Moll Anthony, Mr's Sheridan,
Old Deruane, Polly Mac Garry, John Fagan and Ighne, which were sourced
from 'Visions and Beliefs from the West of Ireland' by Lady Gregory.
Please don't include these people in your searches.

Thanks and good luck.