If you don't draw more than 7' one of my favorite places to get one's act to gether before heading off across Biscay is Chateaulin.
It's 20 miles up the L'Aulne river from Brest. A provincial market town with most things you'll need. The excellent supermarket is 100 yds along the road from the town dock
. There's electric
there and in all the times I've been there I've never had anyone collect money
If you need boat stuff. Marina de Moulin Blanc in Brest has everything to hand.