Did you ever use the Sky Store or the Sky Go service and maybe forgot that you used the service previously ?
If so this guide (step 2) will explain how to retrieve your Sky ID and password.
hi @Anonymous User it is possible that someone registered the email address you have incorrectly, though I appreciate unlikely. If you follow the link in @schnapps post you should be able to identify the Sky ID linked to the email address you have provided. Let us know what happens when you follow that link.