' managed to get this fixed ok and here's what I did.
1. I took the database OFFLINE.
2. In windows explorer copied the files to a different drive.
3. Deleted the OFFLINE database.
4. create a new db with the same name.
5. detach this db.
6. Deleted the files of the detached db.
7. Copy the original database file back into their original location again.
8. Attach the original db again.
9. Try Set up of replication again
Success
It may have been something screwed up in the master db but it's all sorted now.