Ok, we have put the fuel cleaner in to clean this as it brings up a light on the dash when it needs cleaning.
This has been done a couple of times now since purchasing and it made a big difference on fuel consumption and power. This is totally different, its just like the old transits used to be when the pump was putting too much diesel through and they burnt it off 
The Zafira does not light anything on the DPF when carrying out a regeneration cycle and a fuel additive will not clean it either. It needs to go on a good run with the engine upto temperature and the revs above 2000rpm (idealy).
When it starts to regen the fuel consumption will drop and the exhaust system can be heard to drone, this will continue for upto 10 minutes.
If a dash light is coming on then there is a fault code stored which can be read using the pedal trick. This may be a number of things but I would expect either a DPF code or an inlet code (e.g. inlet leak detected).
Either way, read the fault codes and post them up.