Ok - I've balls up big style here.
I updated the _config.php file, but didn't use the newest verison.
This is what is in it now...
$project = 'mysite';
$database = "";
// This line set's the current theme. More themes can be
// downloaded from http://www.silverstripe.com/themes/
My site has since been set-up on a sub domain until it was ready to go live dev.myaddress.com
Do you know how I would alter the _config file to point to the sub domain? Do I need to enter the name of the database in the _config also?
If I then upload the config file again do I do dev/build?flush=1??
Please tell me I've not lost everything - what a nightmare.