Beagle is correct to some extent, The Jindervik never had the D or U designation, nor did the AQM-37 based Stiletto. However there are numerous serial blocks throughout the British Military register that have drones like the Northrop Shelduck (MQM-57A), Northrop Chukar (MQM-74C) and Shorts Skeet that all picked up the 'D' designation sometime in their service. Could be something to do with the fact that the RAF's only drones before Reaper and alike were the 1930/40's Queen Bee (The Army and Navy, plus the RAE (and QinetiQ) have been the main users of drones in the British military throughout the 50's to the modern era).
Leon
The Queen Bee was the target and it was a purpose built drone (it wasn't a standard Tiger Moth modified for unmanned flight, but a mix of DH60 and DH82 airframes with the manned capability for ferry flights and alike). Jindervik's target towing facility was something that was tacked on after it had been in service a few years.