As you're based in Dorset, I'm presuming you won't be covering many motorway miles. With that in mind, a hybrid probably makes the most sense. A Toyota Prius or Auris would be a good purchase. There's the Prius+ too, if you'd like a bit more space. Alternatively, consider a Lexus CT 200h if you'd like something a bit more upmarket. They're all extremely reliable cars with low running costs - hence their popularity with taxi drivers.