www.brittanyferries.co.ukfor travel from Plymouth to Roscoff, Portsmouth to St Malo and other western routes. Brittany Ferries have the routes which take you closest to Trébrivan.
www.europcar.com car hire from Brest airport (you'll need a car to get the most from staying in Trébrivan). We are not recommending Europcar, merely stating that the company has an office at Brest airport which might be useful.
http://www.viaoo29.fr/ : this one allows you to plan a journey within Finistère, you input your departure and arrival points and the site calculates the journey. Very handy, but not every point in Finistere is connected to every other point by public transport, even indirectly, so don't expect miracles!
Weather Forecast for Morlaix (Nearest town with BBC forecast):
http://otguerledan2.chez-alice.fr/: tourist information for the Lac du Guerlédan, the largest lake in Brittany, about 40 minutes by car eastwards from Trébrivan. In French.