At the risk of stating the obvious, the Belfast was touted at the time as the RAF's new strategic freighter (as distinct from the C-130, whose role was tactical).
So I'd be surprised if an airdropping capability was ever contemplated at any stage.
The C-133, similarly, wasn't designed for airdropping (though NASA took the doors off theirs and chucked dummy Apollo capsules out to test their recovery parachutes).