Basically when you want to retire you could buy an annuity

http://www.ft.com/personal-finance/annuity-table

But personally I am not keen on annuities because when you die (or when you and your spouse die) the fund is lost

So if you have a SIPP or similar Pension, Income Drawdown might be better but unless you have a guaranteed income of £20,000 (in which case you can do Flexible Drawdown – meaning you have a lot more freedom over how much pension you can be paid) your pension is capped based on GAD tables.

http://www.hmrc.gov.uk/pensionschemes/gad-tables.htm

I have found an online calculator that makes it easier

http://www.hl.co.uk/pensions/income-drawdown/income-drawdown-calculator

steve@bicknells.net