Hello, I hope the following is of assistance.
Usually if the DPF is causing the engine management light to come on there is a problem where the DPF can't regenerate. If the car does very short trips then sometimes this prevents DPF regeneration which the dealer will do a static regeneration to clean the DPF and reset the warning lamp.
If the fuel consumption is poor and the engine management light comes back on again for a DPF fault this would suggest there is an underlying concern where too much soot is produced from excess fuel for whatever reason.
I would perhaps just ask the dealer why the DPF was blocked, it may also be that the dealer did a software update on the PCM, if this is the case then the fuel consumption may be different until the new adaptive values are learned usually around 600 miles after.
I hope this helps but if I can assist further let me know and I'll reply as soon as I'm able to.
Best wishes and merry Christmas,