GF,
For the US, Cuba was a possibility. So too would Conakary been in range. A quick look at Autoroute (statute miles) shows a central Russian location, over the pole, through Canada, to SAC HQ and then an exit to west Africa was a mere 10000 miles. Back to the USSR was also a possibility.
For the UK it was a simple question of any base in the USSR, they were all within range, but my guess was that the UK would have been targetted by the other bombers such as Badger, Blinder and Backfire where range was far more significant. Still as they had a significant number of ASMs they did not face quite the same threat as the V-Force faced.