I have my inspection later today so will probably learn tomorrow what state mine is actually in.
I note that a growing number of companies are offering services to 'clean' the DPF (and I would imagine this will be a growth market in coming years as the emissions rules have been raised yet again on newest diesel cars).
The treatments seem to involve either
1. DPF removal and clean (which is common for lorries), this would be my ideal if its cheap enough and really does clear out the soot buildup
2. a chemical clean process where the front sensor (just before DPF) is removed so that a pipe can be inserted, then the mechanic injects a foam chemical cocktail into the DPF which is blown through while the engine is running - After this is done the ECU is instructed to perform a DPF clean and you are then given the car back and advised to drive along at about 55mph for 30 mins to complete a normal DPF clean cycle.
to be continued..!