In most cases councils put in CPZs to unify parking in a zone and often the bay times are the same as the CPZ times so if you are in a zone a big clue is the bay times as to when the single yellows are controlled. Councils do not want to deploy CEOs into zones for different times.
While you can't assume totally, if you see say resident bays controlled 8.30am-6.30pm you can be pretty confident a nearby yellow is OK after 6.30pm unless it has its own timeplate with different timing.
One bone of contention is that zones can get too big to be sensibly controlled by entry signs passed some way back and that can be an appeal factor.
Councils should have maps on their websites showing zones and times.
As always, checking before setting off is wise.
One thing - there are some CPZs with no parking bays and just controlled yellows. These may not be included in CPZ maps (yes I'm looking at you, Redbridge).
Another instructive point - where you parked was right by a boundary between two zones - the other zone is controlled for just one hour a day to deter commuters - Barnet is very fond of these as obviously they only need patrolling for one hour a day but still do a good job for residents.
