I've looked for the files in the download section, but I can't find the file that upgrades 5.1 to 5.2. I've found all the rest to go from 5.2 to 5.2.2 and beyond, but I can't find that one. Is this only available on a DVD, or is it available on a separate page?
The upgrade from version 5.1 to 5.2 is a paying one, so that's why the images are not available for download.
You will need to contact your account team to sort this out.