I urge you not to commute a single penny of your pension, however attractive the thought of all those beer tokens is. Statistics show that you are going to draw your pension for a very long time - perhaps as much as 50 years after retirement.
An index-linked half-size pension is not enough to live on comfortably. But an index-linked full pension could be enough especially with a little top-up.
To commute is to gamble. Work out how much you are gambling; £200k? £500K? Probably more. Are you really going to gamble on that scale? I didn't and after 13 years I'm very, very glad I didn't.