Quite an interesting thread for a Sunday morning, however I am afraid some of the posters are a little off the mark; the PC12 and Caravan are both turboprops and therefore require a separate Type Rating, which is more-or-less predicated on having an IR and CPL, so whilst in theory it might be possible to fly these on a PPL in practice it isn't really.
Being realistic, I would have thought the answer to this would be to do a multi rating (I know the question said single, but the course is relatively inexpensive and unlike those above not that onerous for a typical PPL), which opens a few routes to fairly significant aircraft including the BN Islander (there are literally 1 or 2 in the UK you can hire as a PPL).