I think you will find technologies have moved on a tad from Rover days.
My understanding, and only my understanding, is that the Panda (Post 2012) generally uses a Delphi body control module (BCM) that is physically located up under the glove box, accessed, sorry, viewed, by laying in the passenger footwell having gently removed the sound felt that is held in place by a clip. I think if you actually wanted to remove the BCM you may have to get the glove box out of the way? Anyway with the right kit (Zed-full in this case) you can interrogate the BCM via the ODII port and derive the PIN required to then set up the new remotes and, crucially, add them to the BCM list, I added two remotes plus the original, non-remote, Fiat key.
In my research, as I stated earlier, there are claims from folk that they could do this with different kit but this was not the case. Also, the guy I dealt with and was successful said you can take the BCM out remove the eProm and reprogram that, this sounded like rather radical surgery and in my view would be a last resort. Also there was a guy out there on the internet on another forum that claimed to have "cracked" the algorithm used by Fiat to create the PIN (apparently relates to VIN) and would take your VIN and provide a PIN free of charge plus 20 positive contributions or a
donation to that particular forum... Yeah, I didn't fancy that either
One thing that was confirmed was that the ex-500 remote I had could not be reworked; they do appear to be one-shot devices. Although you can swap the blades either by tapping out the roll-pin in the metal blade that is revealed when it is half open (I didn't notice this before) or opening up the whole plastic casing and swapping the assembly.
Anyways my problem is solved for this particular car (63 plate 4x4) that's not to say others haven't been built with Marrelli BCMs etc...