If your income is above a certain level , pensioner/senior or not, pay the tax! If your income is low and entitles you to benefits use them!
The "debates"have been had time and again about fraudulent use of systems..which does happen but it is also a fact that a) many thousands of entitled benefits are not claimed & b) many wealthy people play the tax system too to 'avoid' paying as much as they could &/or illegally withold tax. Both are equally wrong.
Our Welfare State. Is it broken?