Why pay to the Government ???? (via voluntary contributions)
This isn't your only option.

There are many private pension or savings schemes that you can pay into in this country.
Any financial advisor can tell you about them, and go with a reputable company.
... and most will allow you to vary your contributions.

Some will pay a monthly "pension" at retirement age.... whereas others will pay out a lump sum,
which you can use to buy an annuity.