Ok I feel fairly silly now – but just in case anyone else has the same problem, my issue was with the password.
When following the guidelines eg
1 define(‘DB_NAME’, ‘database-name’);
2 define(‘DB_USER’, ‘database-username’);
3 define(‘DB_PASSWORD’, ‘database-password’);
4 define(‘DB_HOST’, ‘localhost’);
I assumed the prefix in the db_name and db_user also had to be there for the password! Maybe not likely to happen to someone else but over the moon that it’s fixed.
Thank you stenrdata and sgarbus for your time