You have published your index page as a .php page
Therefore index.php will show but index.html won't
You either need to change your index page to .html extension and republish (this would mean though that you MUST remove the .php page from the server)
Or just repoint the home page links to .php.
In fact you don't have to point the hom epage links to index at all.
When you link to your homepage all you need is your url
www.travelchains.co.uk