I was informed when I recently took my car for it's MOT that as of 16th Feb 2014 the regulations have changed regarding DPFs and Catalysts.
Any car which is fitted with a Diesel Particulate Filter or Catalyst, as standard, when manufactured, must be fitted with said DPF and or Catalyst when tested. If it is not fitted with the required item(s) it will be deemed to have failed the MOT.
I'm paraphrasing the official looking document my garage showed me. I think everyone should be aware of the change.