I also think there should be some clarification from the IMI, RMI, Motor Codes to the dealers who sell these "unfit for purpose when used in towns" vehicles in the first place.
More should be done to stress the type of use these vehicles should or should not be used for.

It's debateable whether there can be an argument over "if you remove the DPF does your vehicle become a bigger polluter?" as, if you drive twice as far as your neighbour then you are a bigger polluter and that appears to be Ok as you are paying more in fuel tax.

Graham