Just an update. It seems that editing the EP GraphicsCards.sgr and GraphicsRules.sgr files does help with Pets, Seasons, University Life and Supernatural. However, the Late Night, Ambitions and Island Life packs have very different .sgr files so they're proving trickier. The Simmer who is helping me is playing on a new 12" MacBook (I know, amazing!) with the Intel HD 5300 graphics and a Broadwell processor. We copied and pasted the base game files into the EP folders for the EPs they have managed to get to work.
So I'll admit, I really didn't think editing the EP files would make a difference but it apparently does :)
