What's in a week?
While I sympathise, I do not think it is unfair. You have known for a while that changes to pay scales often occur at the beginning of September. If you'd wanted to take advantage of a higher final salary, you could have asked to work beyond your 60th birthday and retire at Christmas. Assuming your pay would have risen by around pound;1,000 from the extra point on the pay spine, the maximum you will have lost in take-home pension is about pound;6 to pound;7.50 per week.