Eh, for most people it's simpler to just use a cash ISA which can provide almost the same rates. Most people don't want or need to carry a huge cash float as opposed to other kinds of investment.
That only works if the capital is already in an ISA or you want to invest less than £20k (soon to be 12k) though. It is common to use gilts to build a gilt ladder to have some level of guaranteed income for older/retired people. This allows you to build your own cheap annuity.
NS&I offer a range of retail products - https://www.nsandi.com/guaranteed-returns is a good option but does NOT come with the tax exemption.