How can it be 'handed back to the Mauritius government' when it never came under its jurisdiction in the first place? It was intentionally excluded from Mauritius as part of the independence agreement. The islanders don't want to be a part of Mauritius, having been poorly treated when evacuated there. They have since resided close by Gatwick, patiently awaiting a return to their homeland.
They would prefer to be a British dependency thereafter, despite being expelled by us. They are about to be disappointed yet again, I fear.