problem with an extremely slow site

I am having a problem with an extremely slow site, its driving me crazy. I have installed WP super cache and WP sanitize and its is still taking forever to load in Firefox. My hosts keep suspending my account and have told to optimize the site,. which I have done following all of the suggestions on this site. ie: , turn the pubin on then off, reduce no of plugins, optimize all images etc.I have been working on this day and night now for over 4 weeks, can someone please help?? https://www.dordogneholidayrental.com

Many thanks