Users not connected with their multisite blogs

Long story short... I had some issues and lost my main database. My recent backup was also corrupted so eventually restored my main site from an older back up and then imported each of the individual Pro Site websites from their own data backups by importing the mssql files.

The only remaining problem is the 'users' don't seem to be connected with the websites at all... it's as though I'm missing a complete table somewhere.

As network admin, I can edit a site and view users, but there's never anything in the list of users.

Strangest of all, if an existing user logins to their own site, their credentials are accepted, but they are told they don't have permission to edit anything.

If I add a new site, the site is created, the user is created, but no emails are sent and the new user is not associated with the new site?

I've tried adding a new user to the existing accounts, but that seems to go no where as well.

Looking at the database, I can't see anything there that links a user to a website, and nothing in the individual site tables for 'users' ... should there be a table for users for each individual site? ie. wp_123_users?

Nothing stands out in the error logs so any suggestions much appreciated!

Thanks in advance...

Matt