I currently pay (salary sacrifice) in to a company final salary pension. It accrues in sixtieths to a maximum of 40/60.
The full amount of accrued sixtieths is payable if one leaves at age 62 (and older, obviously), up from 60 until April this year. One can work as long as medically fit, although by the state of some of my colleagues that's a fairly laxly enforced rule...
If one leaves between the ages of 55 and 62 it is abated, if one leaves before 55 nothing is payable until 55 is reached.
There are a couple of exceptions to the above 'nothing until 55' rule: forced retirement due to ill health, or if one has accrued 30+ years service by the time one leaves.