I think they said the sensor was about £15, but under warranty if valid. The car will eventually go into limp mode to protect itself, haven’t heard of any other suggested methods, so can’t comment. There are companies that will re-map to bypass the DPF, don’t know if it can be done when it is faulty though, I’m sure some-one will comment soon. Take it to SEAT, see what they say, then make a decision. I have heard that a replacement DPF will set you back around £1000. good luck