I just phoned Talk Talk, their router has got only one ethernet port. So as I understand I will need 3 homeplugs; 1 -connect to router, 2 -connect to pc and 3 -connect to ps3. So one ethernet port should do. Please correct me if I am wrong.
And another must be silly question. I assume I don't need wireless desktop network card (unless I want to go wireless) as the homeplugs will do the job.