A collegue traveling by light aircraft across Europe forgot his passport. He had his drivers licence. He called the Irish Dept of Foreign Affairs after landing, who assured him that a driving licence was sufficient for travel within the EU, and left him a 24 hour help line number in case of any problems.
When the French asked for his passport he gave them his drivers licence, and then never passed any comment.
We too are outside the Schengen zone.
dp