Ah, that explains it then, the only file I have is the backup…pretty pointless plugin if you need other files for it to be any use if you lose your site completely. I had been religiously using it to back up every week thinking I would be covered if my site went down !!
I took a clean copy of wp-config.php and inserted my database details into it as well as the keys at the end of the file & when i uploaded it I was able to access WordPress. So the problem is resolved but I am still at a loss as to what caused it, this is the second site that this has happened on (previously I just reloaded WP) could it be a particular plugin that could cause it? Thanks for your help with this problem.