The money the government takes in the form of PAYE or Graduated Pensions, or whatever they're calling it these days isn't 'put aside', it's spent straight away for whatever purpose they deem fit, and your government pension when it comes will be paid from current incomes.
If you supplement your government pension with a pension of your own, and your income from them exceeds your personal tax free allowance, make no mistake you will pay tax mate.
Giok