I can't lay my hands on the stats but I looked at this for other purposes some time ago, and the total tax burden on UK residents is not the highest in Europe.
I believe Sweden, Norway ,Denmark and Germany at least have higher taxation. Although in those cases there is also a more generous welfare system.

State pensions are not actually funded from accrued contributions. They are paid from current revenue. That is because when they were introduced they were paid without people having to wait 30 years or so to qualify.