Reset your logon details
When you purchased your book you received an email receipt from Sagepay (and also from Paypal if you chose to pay using Paypal). These emails contain a purchase reference (invoice ID).
Enter three consecutive characters from the name you used when making the purchase. It doesn't need to be the first three, any three characters from your name will do, as long as they are consecutive.
Your email address is not stored so cannot be used to find your logon details. The only way to find your lost logon details is to use the procedure shown above.