Gaffer
Gibralter and N Ireland a very simlar situations. Ireland was also plantated by the Brits a long time ago. and whilst there are no native Gibratarians rebelling against British occupancy, what's to say that the natives didn't get pushed out to nearby Estapona or the like?
That is as maybe but what will handing control over to the Spanish achieve? Will it right wrongs of the past?

The Spanish came and Raided Mousehole in Cornwall a few hundred years ago. It's still a bit run down. I think it's about time that Spain coughed up for some money to restore the town to it's former glory, right?

As you say, the past is a chicken in the egg question. What's really important is the present and how it will effect people who are alive now. Giving (or sharing) sovereignty with Spain against the wishes of the vast majority of residents of Gibralta is, in my opinion, going to do more harm than good.