You are going to get this warning message appearing all the time, because your 6 mile commute is
FAR too short for any modern diesel engine to properly warm up so that it can 'regenerate' it's particulate filter (i.e burn off all the soot captured by the diesel particulate filter on the exhaust).
It's like trying to do the hoovering when the dust bag is full....it needs to be emptied. The car will burn off all the soot it collects, but only when you're driving it for miles and miles (at fair to high speed) to ensure the engine/exhaust/DPF is scorching hot, in order to burn off the crap.
It is possible to 'force' the car to self regenerate when parked up, however you should just take it for a long drive, keeping revs slightly higher than usual (but keep them at a constant level).
A 6 mile commute won't allow any of that to happen.
Consider trading it in for a T3 or T4 petrol version, which will not have this issue on the same commute.