We'd recommend a Kia Sportage. It's a very comfortable choice, with supportive seats and a high driving position which might help your back. Most models (all but the entry-level '1' trim) come with adjustable lumbar support, which should help too. You might find the standard 1.6 GDi engine to be a bit lethargic but the T-GDi is much zippier. Also consider a diesel - the 1.7-litre's a very efficient engine and might suit your needs if you're regularly covering long journeys.

Also consider a Renault Kadjar. It's similar to a Nissan Qashqai, but majors on comfort. The 1.3 TCe petrol engine is pretty punchy but, again, opt for the 1.5-litre diesel if you cover a lot of miles.