He was obviously illegal but he would have been a lot safer had he climbed up and flew VMC on top (assuming cloud tops not too high etc). That's what I used to do before I got my IR.
10540
He was flying a homebuilt aerobatic bi plane (think it was a baby greatlakes)
So unlikely he had much in there to get VMC on top and remain clear OCAS over the channel.
He probably took off legal VFR in France and was forced down.
Legal VFR? prob not but VMC in sight of the surface yes just.
Pace