Well it turns out that the system manages fine - it just takes whatever subject you give the email and uses that as the event name. So that's that one fixed :-) Not sure why I'd not spotted it before, but there we are.
Edit the day later:
On reflection I'd still quite like to know if what I'm after below is possible. I don't know if everyone knows that their email subject will form the name of the event, and it's possible that you might want to title your email one thing and the event another. Don't really think it's possible though.