There are two things I can think of. One problem might be that somewhere between your laptop and the server a proxy is intercepting your request and passing it along to another IP address than you think. This may be caused by proxy settings in your browser, but some ISPs and corporate networks have a transparent proxy in place which catches all requests to port 80 on the fly.
A second possibility might be that at your hosting company the webserver isn't setup yet to receive connections for the domain mysite.com. That you can access your site via 126.96.36.199/~user is an indication that space has been made available to you to store your script files etc, but to direct requests for mysite.com and www.mysite.com your hosting company has to make an entry in their server configuration which tells them that the files for mysite.com can be found in that project directory.
Thanks Lammert for the reply - I posted this and went to bed in disgust - this monring its working *sigh* ! Last thing I did was change the nameservers over for the domain - and I suppose that may have propgaged in less than 8 hours ....
I am thinking that maybe my new ISP is using a proxy. I don't think it was the hosting company as I've set up many sites there and never seen an issue like it on the web (nor seen something similar reported)