If you have a 400MHz EPIRB with you, definitely, and everybody should have one. But at £600-£1000, very few people going cross-channel will though. I have one in my emergency bag and would hope to grab that on the way out. But if you only just managed to escape in your drysuit, the chances are that you didn't manage to retrieve it...
I carry it in my lifejacket pocket for that reason.
For general reference
www.equipped.com has lots of info on dicthing and equipment and lots of ditching stories.
QDM