Up date . Took car to dealer. They were unable to reset fault light. The reason given was the filter has ash in it above allowed limits and therefore cannot reset the fault. The fix they propose is to take the car back again , use a second car that does not have a fault connect the pressure sense lines from the good car to the pressure switch on the problem car to fool the ecu that a new dpf has been installed and then reset fault , then carry out regeneration and all will be well. They told me this was subaru procedure .
Also advised me that the car could go into limp mode at any time.