Macushla Gary

Hi, I'm newhere and have obtained my first BMW (old 2005 Touring 525i). Iwas using it for 3 days when the alarm went off at 4am in the morning. I went to shut it off but the key had no affect whatsoever and using the key in the doors did nothing. After about 5 or 6 cycles of the alarm going it finally stopped. So I got in the car and tried the key in the ignition. At first I just got a load of 'clicking' sounds with flickering dashboard lights when trying the key but after a few attempts the whole car went completely and utterly dead?? The battery did not seem weak at the time so I am really baffled as to whats gone on. I did read that if you attempt to start the car with a dodgy Fob a certain amount of times the car will shut-down or something (?) but I can find no evidence of this elsewhere or what I can do to get power back etc.. I have sent the Fob off for repair (due back today) as it did not even have a battery inside the Fob!! The car had been running perfectly for 3 days before this happened..any ideas on my situation or what has happened would be brilliant and any cure to get things back-up and running would leave me eternally grateful guys? Gary.