Thanks for your replies.. However I tried the fix from Aaronhockey and it didn't work so I had to use a messy workaround...
I am using a Wysiwyg editor called Prophoto to do the website. So rather than set the menu to be centre aligned as I wanted I set it to left aligned and then used custom CSS to overwrite the padding to push the menu into the centre... If anyone knows a better way of doing this please reply..