Yes, thanks dkarp - I worked this out earlier today with some help from jholder via a specific N95 thread -
Nokia N95.
In summary, you need to have 4.5.6 and add the /ni switch after the domain part of the username; eg:
username@domain.com/ni (this wasn't obvious from some of the available information).
As I wrote in the above post, while it is good to get this working, the IMAP idle functionality is a key feature for phones/handhelds as it would provide push email.
So I'm still very keen to test the new interface - is there a test site somewhere running the new interface which I could test using my N95? This would give me full access to my email, calender et al.