The Santa Fe has a 2.2l Diesel engine. You could also consider the Rav4, Freelander, Honda CRV (all 2.2l) or Mitsubishi Outlander 2.0D. All have good diesel engines that will give 35 to 40mpg in mixed driving conditions. All should be fairly reliable as well and cost approx 37-43k depending on the spec.
My Rav 4 2.2 D4D is averaging around 45mpg on mixed driving conditions. Its very comfortable on long journeys and I have plenty of boot space for buggy, shopping etc.