You can use annuity tables to help you find the best annuities. The FSA publish annuity table on their website and these FSA tables show the rates and companies that have the best rates.
Annuity tables are some help, there is no substitute however for using the open market option to shop around for the best annuities. Using a broker or independent financial adviser who will search the entire market and this will include all the specialist annuity providers that have enhanced annuities. The annuity tables and FSA tables only give you a guide, you really need to make sure you get some help and advice.
The Financial Services Authority, FSA tables are provided by Defaqto and show examples of rates for given set of selectable options you can choose. These fsa tables are again just a guide and should never be a substitute for full financial advice.