I actually found the email address associated with my Blockchain.com wallet (it was the one I thought it was all along and I found the confirmation emails from Blockchain upon set up) This is a functional email but wasn't working on the Blockchain login. After much discussion with Blockchain support, they searched using my wallet ID.

They said this ID is linked to an email address which definitely isn't mine (they didn't give me the full address but a couple of letters)

Should I assume that my wallet has been hacked and that the hackers changed the email address?

I have no idea what to do now. Do Blockchain have a fraud department?

I have the set up email address and all security info.