So this has been marked as resolved but I have still been fighting with a reliable way to center the top-menu when site-branding has been set to display: none; for ages now.
With the help of this page I think I have finally cracked it:
http://matthewjamestaylor.com/blog/beautiful-css-centered-menus-no-hacks-full-cross-browser-support
In case anyone visits here looking for an answer, this is what works for me (placed in custom-css):
.main-navigation {
float:left;
width:100%;
overflow:hidden;
position:relative;
}
.main-navigation ul {
clear:left;
float:left;
list-style:none;
margin:0;
padding:0;
position:relative;
left:50%;
text-align:center;
}
.main-navigation ul li {
display:block;
float:left;
list-style:none;
margin:0;
padding:0;
position:relative;
right:50%;
padding: 10px 10px;
}
Hopefully this might help someone.