All site pages now display blank page

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Hi guys,
First post here.
Been trawling the site for anyone else in the same situation and have been unable to find.

I have been editing the working site today - created a new page and added a background image.
So far so good and operational but not published.

I currently host the site with 123reg (bad choice) and any images that are uploaded via the filemanager need to have there permissions changed (i do this via filezilla) to 755 before they will display.

I changed the latest image uploaded /files/ permissions to 755
and for some reason I changes the /files/cache folder (&subfolders) permissions to 755 as well.

I now get a completely blank page when I try to load the site. I've tried different machines, cleared browers cache iPhone running 3G connection all show a blank page - As if the DNS is not correct However Nameservers are as they should be.

Any ideas?
Thanks in advance