Hi Your alarm panel is locked by the initial installer.There is no way you can resolve this problem other than returning the unit to Texecom. It would be far lower cost to go and purchase a new Veritas PCB Board at around £20.00. Try Enterprise distribution or ADi Gardeniers. The PCB will have the model name on it and you can tell the supplier the info to ensure you get the right PCB board, If your alarm is a blank panel with a separate keypad. See the panel has a V5 sticker on it. If so buy a new Veritas R8 panel PCB. Make sure mains electric is off and the battery is disconnected. Then simply swop each wire one by one into the new board. - Take your time job is well easy. Just before you go to all that trouble - it looks like the way you explained how you defaulted the panel may be incorrect slightly. Full removal of power to the alarm panel. mains power up, press the RESET key on the key pad a good number of times until the panel beeps then use 4321 to silence then try 1234 - then your panel is defo defaulted. If it is a V5 old version programming is different. engineer code then 00 ie 123400 then the key pad lights up. 01 to change user one code.
Good luck Pal
Mark
May 2011