Delete the site from iis. Delete the website folder from the drive and also delete the user for the website from the users under computer managenent.  I would also check in the mysql db that there is no leftover info left in rhe domains and users tables

That was the first thing I tried, except no db. Still doesn't work. Unfortunately can't try anymore as need to get the site up, so its been manually added via IIS. Not a great solution unfortunately.