Getting 404 Errors on backend and frontend

My site is http://www.scapabreakwaterapartment.co.uk

Tonight I added my site to Google Webmaster Tools using the instructions provided on the namecheap site as that is who my domain is with (https://www.namecheap.com/support/knowledgebase/article.aspx/9252). Now I can’t access the site through the front or backend. Whenever I type the url in it comes up as Error 404. I can only assume that these two things are related because I’ve had no issues and have never received a 404 Error before. It literally happened right after I followed the instructions through Namecheap. Does anyone have any advice? Any help is most appreciated!!!