It appears that if you place a key-remote from another car in close proximity then that can "corrupt" the signal from the Subaru Outback key. I placed my wife's Skoda's remote on the same ring as my Subaru key which was then disabled. The Skoda key was removed and within a day the Outback's remote revived itself and now works perfectly. Also, the multi-function display has come back to life concurrently so it seems the two items are inter-related. Weird but there you are. Thank you all for all your comments and theories - oh, wait, there were none ...