Then you need to contact Abacus Car Alarms (link in previous post). You'll need to remove the alarm ECU and send it to them. In return you'll get your alarm ECU back with 2 fobs and a Meta code card from around £99. Think the service takes around 24hrs.
Is your car a Phase1. Think you have a Scorpion 918U alarm fitted and the alarm ECU lives behind the instrument cluster. Not sure if you can get a new remote, but I could be mistaken.
I agree I think Mitch166 has the Scorpion Alarm.
The combined alarm/ siren unit on my phase 1 was under the plastic cover on right/ driver's side under the bonnet, behind the headlight unit - on later cars only the siren is mounted here with the Alarm unit in the cockpit
I contacted Scorpion, they informed me that the alarm unit was obsolete and they did not have replacement fobs, nor any spare parts, nor even wiring/ installation diagrams