Greetings,
I understand the original question has long since been answered but as this is a discussion group please accept my two cents.
I am not certain but didn't the Celts marry by the calendar? In particular marriages and formal courting were done in conjuntion with the Beltaine festival. A marriage could be for as little as one year. Celtic women unlike most had the ability to divorce without the spouse's agreement.
The year long marriage or marriage trial was still practiced in Ireland through the middle of the last century.
Celtics prized freedom above all things and a member of one tribe could not claim for any reason the liberty of another member of the tribe. So in the case of the tradesman's debt at worst is the warrior had pressed his claim the tradesman himself would have been bound in servitude to the warrior for such time as it took for the debt to be paid.
Of course my point is made on Celtic law before the Romans. Though many things about the Celts remained unchanged throughout history some did and in the case of women libertys were lost.