Thanks for the replies guys
Have been in contact with customer services after a very long wait and been told there is a technical problem (as if I didn't know lol)
Anyway. I have been able to access my mail via the webmail.ntlworld.com address quoted elsewhere but it's a bit of a fiddle as the passwords aren't stored apparently so one has to be entered for each address viewed.
As for the login/logout palaver - at the moment it's looking like a retrograde step to me - even the CS person I spoke to couldn't really explain it and in what way it is an improvement. From what little of it I've seen it is a pain in the bum and I can only conclude that NTL doesn't want customers to use it!
There's an old maxim: don't fix what isn't broken!