Sorry Manxman, like a lot of people on the Island you are under the impression that the runway extension will allow larger aircraft to operate from the Island, the extension is in fact an extension of the safety "run off" area which is too short at present.
The airport has two options extend the run off area leaving the runway length the same, or extend the run off area and reduce the length of the runway, so the result of the current review could be a shorter runway.