Annuity rates vary a great deal, and can change rapidly in line with economic conditions. As people have started to live longer annuity rates have fallen sharply. If you want a survivor's pension the rate will depend not just on your age, but your partner's too. Newspapers often have tables that give up-to-date annuity rates in their personal finance section.
Having given all those health warnings these figures (taken from the Regulator's Guide) give a rough idea of how much pension you might get as a male non-smoker aged 65 for a £30,000 pensions pot. (These figures date from 2011 and you are likely to find that current figures are very much lower.)
This should give you a sense of how much rates can vary depending on how you structure your annuity. They also show once again that to get even a very modest pension on top of your state pension you need a big pensions pot.
You can use the comparative tables on the Money Advice Service website to look at how much you might get from your pension pot.