Upgrading to 1.5 theme - disaster - NOW SORTED

[firstforward]

I have installed the latest version of PS and after keying in mountains of data decided up upgrade to the latest default theme:http://addons.prestashop.com/en/neutral/3337-prestashop-template-15.html

 

Trouble is the upgrade went wrong and I appeared to have the new and old theme corrupted with some of each appearing in both new and old theme, then when I tried to switch back to the new installed theme the main page stayed blank. The old theme was so unusable I decided to delete the entire site and copied back a very recent backup I have on my PC via FTP.

 

I still have a blank page and cannot access the admin section with more blank screens, have I assumed incorrectly that this is all I needed to do if indeed I shoud have done it this way at all.

 

 

Installed new shop and imported all items in.