Thanks for pointing me in the right direction Simon. I have got this working using your html and the following css (at least in Safari and Firefox it works as intended):
.title .logo-big {
display: none;
}
.brand-header {
margin-bottom:-63px;
}
.brand-header .brand-logo {
z-index:5000;
position: relative;
left:130px;
}
As you can see here: http://forum.open-dialogue.net/t/ta-da/15