You need to decide on the level of security you want as the main characteristic of a typical annuity is that the income is guaranteed. If you want some investment exposure then you can purchase a unit-linked or with-profits annuity, however the income is non-guaranteed. Once you reach the minimum pension age (currently 55 and it is intended that the minimum pension age will increase to 57 from 2028) you have the right to buy an annuity from your current pension provider or from the open market.