MY99 Wagon
Have downloaded the re-programming instructions which state that after fully arming system you should then disarm and enter programming code into keypad - each No. being confirmed with a single led flash from keypad. I have tried and tried but no joy - the LED flashes a few times at me every time I try entering digits. What am I doing wrong???
Help very much appreciated.

if you press the buttons too 'slowly' it wont work. The flashing LED indicates an unexpected button press Theres a bit of a knack to it, you need to 'jab, at the button fairly firmly but quickly, and dont press the next button to soon/late after that.
Do you have the earlier keypad with the flush buttons or the later, raised type?. If the former, using a BLUNT prodder helps: the rubbesr on end of a pencil is ideal.
Are you remembering the * and #? in the programming code?