Voyage of the Sparrowhawk by Natasha Farrant

In the aftermath of World War One, everyone is trying to rebuild their lives. If Ben is to avoid being sent back to the orphanage, he needs to find his brother Sam, wounded in action and is now missing. Lotti's horrible aunt and uncle want to send her away to boarding-school (when she has just so successfully managed to get expelled from her last one!) And Clara, their young teacher, is waiting for news of her missing fiance.

Just as they think they've found their feet in the new order, disaster strikes, and Lotti and Ben must get away. And so they hatch a plan - to cross the Channel on Ben's narrowboat and find Sam. And there's something in France that Lotti is looking for, too...

Buffeted by storms, chased by the police, Lotti, Ben, Clara and a growing number of dogs set out on an epic journey, on the search for lost loved ones and a place to call home.