I'd believe that to be true if it wasn't for the fact that my existing install happily talks to the mySQL server. That's why i wondered if it was duff environmental variable settings somewhere that the install scripts were picking up instead of using the connection information. It certainly passed the connection test part of the install process - this failure is at the point of completing the set-up of the admin account and table creation steps.

I guess i could do a local install onto a laptop (to see the config) or i wonder if i can perform the install without running the install.php? i.e. hack it about piecemeal fashion to force it to use the proper connections.