Hi Peter
You've probably sorted this by now but I'll feedback in case anyone else has same issue.
To upgrade the firmware you must have a panel that is in the "Premier Elite" family. As long as it is, then the chipset allows upgrading.
Most people want to upgrade to V4 or above so they can connect a SmartCom and use the wireless features and app on their phones.
For that I use the Texecom Serial to TTL (small white 5 pin plug with pin 2 missing) and back everything up to Wintex first. That means you can't lose any settings - and you'll need them later anyway when you push the configuration back once the firmware is updated.
Once you have the panel backed up, connect to the flasher interface - I made my own as they are a bit expensive and prices do vary - ebay item 333727230395 is my take on the interface.
Download the Premier Elite Flasher software from the Texecom site and follow the instructions.
It will take about 3-4 minutes to upgrade to the latest firmware and then you've ready for an NVM reset and load back the settings from Wintex.
Bit of a faff but does get you up and running on a SmartCom!