Spike, I have read in some posts that you were good looking for information. And I confirm 100% that it is.This old post seems to confirm your findings from the Spanish Forum - https://www.a2oc.net/community/index.php?threads/retro-fit-remote-central-locking.39929/post-355298
Plus lots of info in this thread which may be helpful - https://www.a2oc.net/community/index.php?threads/hi-all-from-barcelona.24354/post-206977
The CCCU will reject the coding (i.e. it will not save) if the required hardware for that coding is not present.I acces module 46, modified the coding to 06768 (originally it was 02048) and pressing "do it!". The issue is that the new value was not saved.