when i signed up over the phone bt automatically created the email address for me which i do not like can i delete this and create a new 1 and if so how ?
You can create a sub account with your preferred address, and use that instead. You can re-direct any existing mail to the new address, until you have informed everyone.
You cannot change the primary e-mail account name, only BT can do that. You need your primary account details if you want to use the free BT Wifi.
Further to Keiths reply here is a link about how to set up sub accounts.