Bear in mind that during the design stages of the Arrow they were already looking at increasing its range with subsequent versions! The flyers seem to have something like 1100 KM range -with no images of any with either probes or tanks it looks decidedly slim on range!

To operate an Arrow in the U.K would have taken a massive security operation to achieve little. Seems to me that it would have been far easier to send some test pilots out to Canada to fly it rather than risk a development aircraft on a long transatlantic journey which could have ended with either loosing it at sea or going tech at some airfield en route !

It makes a nice seasonal conspiracy theory but not much of it stands up to examination!