Bongo Fury

I've just bought a 1997 Bongo fitted with a Meta System immobiliser. It's worked well for a couple of weeks but on a frosty day last week it let me into the van and started the engine fine, then suddenly the alarms went off. I turned off the engine and silenced the alarm but since then attempting to restart has been impossible. When trying this all the instrument indicators vibrate on and off but no start up. This is probably a question for Meta Systems but may have a simple answer from a Bongo afficianado. I've heard of various Bongo owners having problems with immobilisers? Are they capable of being dismantled? And advice gratefully received.
Sessapit

Sorry if this is a silly question but is the battery OK? Cold weather will reduce the available power and could make the immobiliser reset/panic/alarm etc - and may explain why it won't start any more?