If you read French, this one seems pretty good.
http://perso.orange.fr/histoire-bretagne/Fichiers HTML/chronologie.htm
The whole site is an initiative by the local Breton authorities. It briefly summarizes how... Breizh... if you wish (from now on I expect you to consistently refer to Wales as Cymru

) ) managed to juggle English and French influence and trade a relative freedom (staying out wars) into economic prosperity in the late Middle Ages. That seems to have given the Bretons a strong national heritage to pit against the French influence.
One of the reasons... Breizh... kept more of its language than say the... Cymru... was that it was that industrialisation left it as a backwater. Wales (oh, I know it's an imperialistic misnomer, but bear with me

) on the other hand was one of the very first parts of the British Islands to industrialize, and that meant an huge influx of Englishmen in the south as there was a shortage of labour.
The Bretons did get an entirely indigenous demographic boost in the 19th century and could export people (dirt poor and starving), while the "heartland" remained occupied with sailing, fishing and agriculture. That still left it to deal with the concentrated effort of the French state to kill off the language, very similar to the "Welsh Not" campaign, I might add.