I have to sympathise with Colin on this one. Modern cars may be cheaper to buy in real terms now but the cost of repairing has gone through the roof. I can easily give someone a bill for £400 and find about £50 in my own pocket. I have never yet been able to sell someone a genuine cat in spite of the warnings I give them. I recently told a customer that the dpf on a Volvo (can't remember model but it had the 1.6 psa engine) was a service item at 75K so she sold the car! Another thing is trying to convince people that a modern diesel is no good for doing the school run. If I did everything "by the book" I would soon get a reputation as the most expensive garage in town. In answer to one of your questions Colin, I think many people have cleaned dpf's successfully using traffic film remover or similar.
Regards,
Bryan.