Hi Neil,
I saw your posting when I had to locate the SQL download link myself for a customer remote installation. Sometines locating files on the Dynamics site is unnecessarily conplex, and the site indexing doesn't always provide the most appropriate links.
Searching the Microsoft Partnersource site for "SQL Runtime" will provide you links to a series of documents that describe Microsoft's current terms for runtime licenses. A couple of those documents themselves contain links to the various versions (23 bit and 64 bit) and languages for downloading SQL2012. I noted from your personal info that you appear to work for an end-user organization, and I don't know if the Customersource site contains links to those documents and files. You may need to contact your reseller to obtain the SQL download on your behalf. I copied the relevant section from the SQL download page that would apply.
SQL Server 2012 Standard Edition (Runtime) softwareis only available via download and is not availableas physical media. The software may not be
distributed to customers and must be deployed by the partner. Partners are responsible for complying withthe terms of the program.