You are doing a phenomenal mileage and, because of that, mpg is critical. I don't think you can do better than your Captur with its familiar Renault 1.5DCI diesel engine. If you wanted to cut purchase costs a bit you could consider a Dacia Logan MCV estate with the Renault 1.5 DCI engine. Or, of course, a Dacia Duster, which has just been revised. Since the engines and transmissions in the Dacia are almost exactly the same as in the Captur, there is no reason for the difference in service intervals, even though, in spite of your huge annual mileage 10,000 - 12,000 miles is more sensible to preserver the life of the engine long-term.