Why an earlier Nimrod barely changes Soviet planning

How would the Soviet Union react if the RAF acquired Nimrod in 1962 or 1964?

Probably very little, unless Britain bought an unusually large fleet, because Soviet plans were already driven mainly by American and aggregate allied air power.

The RAF acquiring Nimrod in 1962 or 1964 would prompt little Soviet change. Soviet planners were already building against the primary American aviation threat and treating other allied aircraft as part of the same total. A very large British purchase might affect quantities at the margin. Otherwise, an earlier service entry would not alter the best capabilities Soviet industry was already trying to field.