CPI for September was 0.5%.
If your pension is not yet in payment, the earliest you can access an AFPS 75 pension is age 60. For AFPS 05 the 'normal' preserved pension age is 65 and for AFPS 15 it is the member's state pension age - but they can draw it at any age from 55 onwards at a reduced rate. In all cases the claim is all or nothing - you cannot just take a lump sum. The only time you can get your pension paid before the ages I have given is in the event of permanent ill health preventing full time work.
If your pension is in payment, HMRC rules prevent the scheme from reducing your pension. That means that you could not (even if the rules permitted it) take a lump sum at as it would mean the pension reducing to pay for it.