If all you care about is cheap to run, then get a bubble shape Micra or the equivalent Yaris.
Had my craptactular Micra for 5.5 years now (will change if I ever leave University!) and all that has gone wrong with it that cost me money is the driver's window wouldn't wind up (1 hour labour -Only 'cos I didn't have the correct adhesive).
The Micra I have is only worth about £800, which is why I am reluctant to get rid of it, because everything works.
Most old cars will be being sold because something big is on its way out on them.
Nothing wrong with the Micra, Fiesta or Yaris. All can come with air con but keep your options and buy on condition. Most old cars will be being sold because something big is on its way out on them.