Update: apparently I jinxed it when I said time will tell. The squealing is back.
My 2015 4x4 is currently with Palmers of Watford for the squealing rear brake problem. They say they haven't heard of any re-call/upgrade for the rear brakes. I have just emailed them the forum thread so they can see the various comments and damper fix. Will let you all know how I get on. Incidentally it also had the dash battery warning light coming on randomly when driving at 50-60mph and a loss of power steering. They found a fault with the alternator and are replacing it, I have always had good service from them previously (on my third panda) so confident they will get it sorted.
My 4x4 has gone in this morning and the problem has been confirmed by dealer who has ordered dampening kit, shame Fiat technical are insisting on turning it into a two day task.
The chap who's dealing with me said it only seemed to be 4 wheel drive models (I suppose that could / would include the Cross). That might not be gospel though. Do all the 2wd models have rear disc brakes or drums (I don't know)? Could that account for a higher percentage of 4x4s?
M