On the BomberCommandmuseumarchives.ca, it mentions that the Leslie Howard flight was due to stop at Chivenor to refuel, and that 407 squadron ground crew were awaiting it. I have not seen that info anywhere else and it doesnt appear in the 407 squadron ORB. While not an unknown occurrence to stop off there as evidenced by the August 1943 logbook page in the thread, and while theres no doubt Whitchurch was the final destination, I run a facebook history group for wartime Chivenor and would make a good story if it was confirmed