Sorry, we found some problems with the information you entered. We've highlighted the relevant sections. Please check and resubmit.
Add Domain Name
Domain name already in use
If you look slightly further down the page you'll see that www.msera.org.uk has already been added the last time you filled in the form.
At this point you need to update your DNS settings as per the document I linked above and the service will automatically start serving your site for that domain.
I hope this helps.
Cambridge Open Systems Support Team