Brittany is glorious in summer, when the weather is often warmer than in other parts of northern Europe, though it can be packed with tourists. Come in spring or autumn instead and you’ll have miles of sandy beach to yourselves. Don’t rule out visits during the colder months, either - the countryside is beautiful, and there are plenty of opportunities for blustery coastal walks.
There are a few festivals which are worth catching if you can. These include a jazz festival in Vannes in July, Dinan’s medieval-themed Fête des Remparts every other July, and the famous Inter-Celtic Festival in Lorient in early August, when representatives from all over the Celtic world congregate for cultural performances and parades.
NB, please do not rely solely on this information for your travel plans.
BRITTANY: BY AIR
From the UK: carriers include Flybe, British Airways, Air France, easyJet and Ryanair.
Alternatively you can fly to Paris, then get the train to Brittany (see below).
Within Europe: try Aer Lingus, Air France, Iberia, Vueling, easyJet and Ryanair.
From the USA: fly to Paris then catch the train, or take a domestic flight with Air France or easyJet.
By train from the UK: take the Eurostar from London to Paris, and then get the TGV from Paris to Rennes, Lorient or Saint-Malo. See Seat 61 for more details.
By boat from the UK: You can sail to Saint-Malo from Poole or Weymouth with Condor Ferries, or from Portsmouth with Brittany Ferries. It's also easy to reach Brittany from southwest England, using the Plymouth to Roscoff crossing with Brittany Ferries.
By boat from Ireland: Brittany Ferries sails from Cork to Roscoff, or you can go from Rosslare to Roscoff with Irish Ferries.