Thanks Cliff, though I partly disagree. Having spoken to a number of dealers there's a consensus that a petrol Q5 is 'very thirsty', so I'm not sure a 20 minute blast in a diesel would be enough to offset the cost between the 2. Whether or not it would solve the DPF issue, I'll defer to you as I am not that well informed on the matter.
Ref the hybrid whilst it's a good suggestion, I am not sure it's any different to a petrol to be honest, and perhaps even worse. The official range for a Q5 PHEV is around 26 miles so in the real world that's likely to be around 20 at best. That's not enough to even cover my daily commute to work on a full charge which means that for some proportion of the journey I'd be driving a petrol with the added burden of a massively heavy battery. I am not sure that's a great solution.
I do have the concerns about the diesel/DPF issue which is a real shame as the Q5 would be my preference, all told.