You can buy top-up years for your State Pension if you don't have a full entitlement - best done once you have decided to stop paid employment so you don't buy more than required, and take advice form a contributions expert at the DWP.
You can also use your savings to buy an annuity, not just a pension pot. But of course you won't get the benefit of the 20% tax relief payments on the savings before you put it into an annuity.
If you're not working, you can still drip feed savings into a DC pension - up to £2880 each financial year which will still receive the government top-up tax relief payment to £3600, so this might be worth doing if you decide to choose an annuity eventually. Also have a look at immediate vesting pensions if you have savings.
It is a bit of a misconception that annuities are a fixed amount for life (at one time perhaps). They can be much more flexible now depending on the product you choose. You can get fixed term ones, index linked ones, and variable rate ones - which are invested and you receive a variable amount depending on how the investments perform, but with a guaranteed minimum income.
It's important to shop around though as providers vary quite considerably on the returns they offer - it's not a standard amount. I rarely think it's worth paying for a financial adviser in most circumstances, but in the case of buying an annuity it's to be recommended. Once you have bought an annuity you can't change your mind. (I am not a financial adviser - so always do your own research).
You mention downsizing. This might well be a suitable option depending on your circumstances. I would suggest when the time comes you also do consider equity release schemes, if you don't want to move. They are now very well regulated, and many mainstream lenders offer them with attractive safeguards and flexible terms. I know many people are very wary of them because of the past scandals, but the products on offer now are very much improved and worth investigating. It might not be suitable at all for your situation, but I would say keep an open mind until you have found out what is available.