D and D can and do triangulate on 121.5
If I was really mid channel, I would squawk 7700 and call Lille on 120.27
Lille has powerful primary and secondary radar that can see low down all the way across the Channel. More importantly Lille can scramble the French Securité Civile Chopper which spends its time between Calais and Le Touquet. The combination of your 7700-derived position and the extreme proximity of the French chopper give you a far better chance of being rescued quickly than any other course of action.
Make sure you ditch near a ship. There are normally plenty to aim at.
2D