In this price bracket you generally going to be able to avoid diesels with diesel particulate filters so diesels are the sensible choice. A current shape CR-V 2.2iCTDI would be 5 years old and mileagy for the money, but is the nicest car.

Late old-shape X-Trail 2.2 diesels could also go on the list because by 2006/2007 problems were solved. A Qashqai with a big enough motor is more than your budget and anyway had DPF problems. Very hard to find a RAV-4 2.2 diesel for £7k and they too have DPFs.