RW
You are the second person who has been told by JC+ that they would lose their PIP on transfer to UC! PIP and UC are separate benefits and are both claimable at the same time.
At this time, ESA claimants cannot be transferred to UC even if there claim is reassessed, at some point in time this will change, but the UC project is years behind schedule and even the current dates for this seem unlikely.
There are circumstances where a claimant can be moved to UC following a failed reassessment.
UC only replaces Income Related ESA.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
