Was Fitz ever used on the Continent?

Second hand I received an observation about an entry in Genealogics.

I display Eudon III, Vicomte de Porhoet, died 1234, name of wife unknown.
Source mentioned Georges Martin, "Histoire et Genealogie des maisons de Rohan, Chabot, de Rohan-Chabot", Volume II page 32.

I have now added another source, ES Schwennicke, Volume X Tafel 13.

The observation I received maintains that this person really was known as Eudes Fitz Count or "if you prefer Eudon Fitz Count", and "he doesn't appear to ever have used a title at all".

Two sources are given, Morice 'Memoires pour Servir de Preuves a l'Histoire de Bretagne I (1742)
and
Louis Rosenzweig 'Cartulaire general de Morbihan I (1895) : 206, 209-210, 215-216 (charters of Eudes Fitz Count ("Eudo filius Comitis") dated 1221, 1225, and 1231), 223-225.

If in a chart someone is called in Latin filius Comitis, should that be translated to Fitz Count? Especially as it applies to someone living in Brittany?

ES Schwennicke Volume X Tafel 13 to 24 (Tafels 13 to 24 cover the de Rohan family), shows quite a list of sources, the second source given is Georges Martin, the source on Genealogics.
Neither Morice or Rosenzweig are mentioned.

Georges Martin gives two pages with sources and those two are not mentioned either.

Georges Martin in his book explicitly mentions him as Eudon III, vicomte de Porhoet.

Schwennicke calls him Eudon III, comte de Porhoet.

I presume Eudes is French and Eudon the Breton form of that name, but as both sources use Eudon I think I should stick with Eudon. Neither Georges Martin nor ES display FitzCount or filius Comitis, and so I think I should not use that either.

Also I was told that Eudon's wife was a Marguerite, but neither Georges Marton nor ES mention a wife and so I feel I should keep the entry as I have it.

Can anyone confirm that Fitz Count is a valid naming on the continent in the 1200s?

Leo van de Pas
Canberra, Australia