So much misinformation and downright wrong information on this thread!
To clear up a few things - if you are involved in a RTA and sustain injury, and the RTA was caused by the negligence of another driver, any claim is made to that drivers insurance company. Not your own insurance - your insurers will only deal with your vehicle, and with the claims of any passengers in your car if you were at fault for the collision.
Winns are a fairly slick operation, we deal with them a lot. They are difficult to deal with but generally get good results. It's very rare for them to run a case all the way to trial and then abandon it at the 11th hour. I think we may only have half the story here...in particular this sounds to me like the other side had evidence of fundamental dishonesty or similar.
Just to be clear, was liability admitted? If not, are you absolutely certain you correctly identified the car and driver? Were you able to describe the other driver? What did the driver say in their witness statement - did they deny being there, or deny that any impact occurred?
It's possible that there's a issue around identification but I would have expected that to be raised much earlier on. So I am leaning more to possible FD, that there is evidence to indicate you have lied about the accident or exaggerated your injuries.
On what basis exactly did Winns say you needed to drop the case? Was reference made to any new evidence being disclosed?