Update: Hooray, the British-English translation of Agenda is now available as part of Agenda version 11.0 
We’d invite everybody to give it a try and let us know if you find any aspects that can be improved, need to be corrected, or are giving issue. Join me in thanking @unexpectedly who worked so hard and with so much passion to add the British English translation of Agenda, even helping us correct a number of errors in the US English version as well! 