To upgrade the core game only you need to select the 'Returning Crew' pledge at £28.
However if you bought at retail then you will also need to purchase the 'Redeemers of Purpose' Add-on for the miniatures, unless you are happy to play with proxy miniatures (the £28 upgrade includes the 'Redeemers of Purpose' box, dashboard, preacher card deck, and radar tokens. You will also receive The Geneticist dashboard. At the moment The Geneticist is not available as an add-on but we may make this available during the campaign which would allow you to also purchase this miniature to complete the set.
If you bought all the add-ons at version one than you simply need to select the 'Returning Crew All-in' Pledge and swap in and swap out new elements.