Here are a couple of links that might be useful if anyone else has this issue.
First one describes someone's hassles and shows it was sorted under warranty (mines finished unfortunately...)
2nd one is a tech note from Subaru Australia, describes flow charts and diagnostics etc as well as a last ditch way to solve, and other tech info.
http://www.whatcar.com/car-news/subaru-outback-dpf-fault/1217936
http://www.subaruoutback.org/forums/attachments/gen-3-2005-2009/19290d1301087520-dpf-subaru_dpf_workshop_advice.pdf
If mines truly knackered, the main issue I have is that I didn't get a proper warning. On Thursday the DPF light came on (indicating 85%blocked), on Friday I was going to do a long run to try and clear it but the light was flashing ( indicating 100% blocked), then 5 mins later the other lights came on (indicating 135% blocked and in limp home mode!).
Hopefully that all indicates a sensor problem?