Fish text is a SMS provider of free texts as listed a few months ago by Zaheerhttp://www.hotukdeals.com/item/292371/send-text-messages-over-gprs-for-2-/
However you can register for free and you instantly get 20p worth of credit (10 free texts). However texts sent from the fish text application to another fishtext user are completely free and unlimited. Despite the fact this is a damn good service at just 2p per message.
I am currently trying to test the application so I will let you know how the free text works once I know