bugger, have you tried turning the ignition switch on and immediately pressing both indicators to see if you can enter the pin? maybe give that a go mate
At this stage mate, I'd be replacing your battery. Think you said it was at least 7yrs old. Check all your earth connections on the frame and battery also.
have you checked the 9 volt alarm battery? or both brake switches and brake light bulb just a couple of random thoughts
Mick, probably a stupid question, but feeling for ya mate, you've had the fob with a new battery in it on you when trying to start it? maybe you accidentally put it in transport mode when the alarm was going off?