Well it was kinda crazy. I've literally just managed to fix it, which is a shame with your answer 'n all.
It turns out CPanel has a grudge against MyPhpAdmin, so they cannot work at the same time. And in order to get the MySQL user to work for Drupal without using MyPhpAdmin, I had to add a user of the same privileges, user name and password
twice
So for future reference to anyone who reads this thread, if the install read "Unable to read from <USER>@localhost" or "No write permissions to database <USER>@localhost" or something like that, and you use CPanel, try adding the DB user
twice - it may just work. I'm pleased I randomly tried it.
And I'm loving Drupal 5.0's new look. Tis beautiful
"History shall be kind to me, for I intend to write it" - Winston Churchill