How do I change the registered organisation details and account number on the up graded v7 install?

You need to contact actual EW Support or Sales via e-mail, phone, or opening a support ticket. This forum is essentially Uses helping other Users and none of us can assist in that. Click on the Support link at the upper right hand of this page which has links to open a support ticket, as well as the phone number (and hours it is open), email, etc.