Three volumes have been published in France. The English translation of Long John Silver Vol.2: Neptune will be published here in March 2011. Amazon UK have it available for advance purchase. Long John Silver Vol.3: The Emerald Maze is due later. Neptune won the Prix Saint-Michel in 2009 and The Emerald Maze in 2010.
The French buy many more comics and graphic novels than we do in the UK. I first found Volume 1 in a bookshop in Nantes and was very impressed by the artwork. I thought it was so good that it would be translated for the Anglosphere market.
p.s. Just received my copy of Neptune, the second book in the series. Not as good as Vol.1: Lady Vivian Hastings, either in story or artwork. The book is also poorly made. Several pages came loose in my copy as soon as I opened it.