Fightback
We cannot stress enough that you need to appeal in WRITING against a PIP decision, not over the phone. We know it is tempting to get on the phone as soon as you get the dreaded brown envelope, however this will ensure that they will reconsider the decision using the same evidence that day or a few days later, and will most likely come to exactly the same negative decision as it will not give you adequate time to send anything new in.