I can confirm that, in the Andover C Mk 1, you select reverse during the flare for a short landing. Reverse is selected using the same lever that removes the Flight Fine Pitch Stop after a normal landing (same lever as in the HS748) by pulling it further out and back. It is a "T" handle in between and slightly aft of the throttles. One of the problems is that you need to have your hand on the nosewheel steering tiller when reverse is selected (or when the FFPS stops are removed) in case only one prop goes into reverse! Therefore, careful co-ordination is required between the 2 pilots as the controls must be restrained also during the landing rollout. There is more than one way of doing this. One SOP was for PF to initiate the flare, call "your controls", after which PNF handled the yoke for the remainder of the flare and touchdown, and simultaneously put one hand on the NWS tiller and selected reverse thrust with the other. I was a passenger during one such landing where PF (the Squadron boss) flared too high, called "Your controls" and selected reverse at about 10-20 feet! PNF (the flight commander) afterwards said that he did not know whether to push, pull or reply "Negative, your controls!" After the very spectacular arrival, the cheer from about 20 Andover qualified pilots down the back was VERY loud! We then changed the SOP such that PF kept control of the yoke and tiller and PNF selected reverse on PFs call.
I believe that the PC6 uses reverse in flight to achieve steep descents and that Concorde can also (although it creates a lot of buffet). Can anyone confirm this?