From what I can understand from the responses here, it looks like 'shared host' doesn't work with PS3 if you want to run the installation wizard.
Another thread reply stated WA are now going to put a message up on the PS3 page to indicate this. Let's hope it's very visible and not buried. I would suggest it's the first line of the main PS3 page (with any further esoteric problems), so that other users can email their host company first to ask them specific questions before purchase of PS3.