I also worked for an extra two years (fortunately I was just in time to retire at 65 and miss the change in the retirement age), I reduced my hours to 25 a week, took my state pension & pleasantly surprised that due to paying national insurance received a slightly larger pension than normal, did not have to continue paying NI, so that was a bonus, however, the State pension in the UK is one of the lowest in the western world especially compared to say Germany.
The tax man did not take into account the pension they were paying me so with my earnings over that two years, I owed them quite a large sum of tax by the time they sorted it. Well, you think you are doing well & someone kicks you in the B&££$.
Now fully retired & fortunately had the sense to contribute to a private pension so at the moment can live a reasonable standard of life.