With you saying that the questions have now changed, does this render them useless?
Not useless, unless you are just learning the questions and answers in the hope that will get you through the CAA papers. They are all useful for revision once you have tried to assimilate all the material in any of the ground school book or CD series (Oxford Media, Jeremy Pratt PPL series, Trevor Thom Air Pilot manual series etc.). But for exam prep I would suggest you are undoubtedly better off with the latest version.
Your instructor wil have an opinion, and that's the best person to go for advice.