If the UK is going to get involved in opperations world wide then it needs organic air cover for the fleet , when the last of the "real " aircraft carriers was withdrawn (in the late 70,s ?) the RAF stated that they could supply the air cover to the fleet over most of the globe , its a bit unfortunate that the wars all seem to happen in bits of the globe that the RAF cant reach.
The ships that will be withdrawn are mostly from the over large anti sub warfare fleet that was nessesary during the cold war.
I see it as a major step forward putting the fleet air cover back in the hands of the navy , at the moment the policy is to fit the ship for but not with "cats and traps" but this desision has all the haulmarks of the "through deck cruiser" helicopter carrier that the navy got insted of the replacment aircraft carriers , fortunatly for the falkland islands someone in the admralty had the bright idea of putting the Harrier on the "through deck cruiser".
I predict that it wont be long before the ships are fitted with the "cats and traps" and the fleet gets its real air power back all be it 40 years late.