ok that means it has a DPF. the filter/Eolys fluid needs looking at. This is why you should not buy a diesel. Notoriously fickle. This thing is it's not really the filter iself but the whole electronic/hardware/chemical concoction. Once the ECU has determined It's not working properly it's a nightmare. Anyway this link explains it and there are experts out there. The dealer should know all this but they won't want the expense of sorting it so they are stonewalling, hoping you will go away. See here:
http://www.volvoclub.org.uk/diesel_filter.shtml
also, do go to Volvo UK and moan at them and threaten further publicity unless they sort it