The UK is a whitelisted country; there won't be a problem unless you are using a proxy (never allowed) or an ISP that assigns "offshore" IP addresses...
It's mostly about resource allocation planning. You can still get unlimited space if you need it; see the Disk Space Policy Change thread in the News...
I'm getting about two seconds for the layout and another two-three for assets. (You do have a lot of HTTP requests on the page, between stylesheets,...
I tried your site on Chrome, Iron, Firefox, Safari, and IE10.
None acted the way you described when clicking the "x" to close the authentication pop...