All diesels sold from I think the 1st Jan this year have to have a DPF by law. Prior to that it was dependant on the engine meeting the emission regs, some had them, some didn't. Yours will certainly have one since its a very new model introduced for the 2011 model year.
As an example our 1.6 CRDICeed was registered in September 2010 but is a 2011 model year car, it has a DPF. 2010 model year and earlier 1.6CRDIcars did not have one. All 2.0 CRDI Ceedssold between about 2007 and 2009 (when it was discontinued)had one because the engine would not meet the regs without just like my 2008 BMW diesel. In some EU countries the 1.6 CRDI had a DPF from its introduction.
AllDiesels should be fitted with some sortofDPF now, which makes them Green and tree hunging!!!!!! yep great.
If you drive a good few miles and get the motor really hot, it will clean out the DPF, but a run to the local shops or school trip Not the car of your dreams, you should have got a petrol jobby.
And if you drive less than 10,000 miles you will not get the pay pack a diesel will do.
As long as you don't use the car exclusively for short journeys you shouldn't have any problems. If you do, then as has been said, the petrol option may be the wiser choice, although you will also probably find that the catalytic converter never gets hot enough to function either.
The payback time with a diesel varies from car to car. You won't need to do 10,000 miles in the diesel before you start saving money over the petrol option if said petrol option comes with a 6.1 litre engine, 14 mpg and £450 a year road tax.