2Ds,
Would the French helo cross the FIR though? If you ditched on the British side, I would imagine they would get on the blower to London.
Kolibear,
I am not sure that there is a significant advantage of having other small aircraft looking for you bobbing around in the drink. Once the aircraft has sunk, unless you have a flare, they are very unlikely to spot you. Best get the professionals involved right from the word go and it seems that 121.5 is the way to go.