Well, if it helps, you asked for advice and here is mine:
1) sell it to the club member with the most Italian sounding name
2) stick it on eBay with great pictures with a starting price you would be happy with and see what happens, it's often the best way to determine price
3) keep it, treasure it, look after it and keep it original as it is a beautiful and very special car and an important part of our Fiat 126 history, I did not even know there were any RHD Fiat 126 Black cars left
All the best and good luck with whatever you decide!
BV