Never had this problem since !
Since found out my temps are well down ( via hidden menus ) which means my thermostats are shot which in turn means my car wasnt even attempting to carry out Regens. Which is why my DPF was knackered.
Lesson to all:
Keep a check on your temps. If they are down then get the Main Stat and EGR stat changed. Better to do that than to have to remove / replace the ludicrously priced DPF.