I think it is fair to say that they caused chaos. A form of option "c" above is probably the best answer, not a million miles away from the USN practice od "due regard" though. Their transit flights were not only to Cuba, there was also a detachment at Conakry in West Africa. The Cuba and Conakry aircraft were normally the Bear D, but the Bear F was a regular visitor to the N. Atlantic as well. The Bear D would also come out to observe NATO exercises and sometimes the Badgers (can't recall the model) but they rarely came south of the "gaps".
I am sure that some of the older Shanwick ATCOs might be able to shed a bit more light on the ATC aspect of your question.
Rgds
YS