My remote (STD subaru alarm UK MY99) has stopped working, tried new batteries and nothing (other remote works fine), my question is this - Do I have to re programme the remote once new batteries are fitted or should it be a simple replace and go ???

All you need to do is replace battery(sigma manual)have you tried a battery from the other working remote???you might of bought a faulty battery.
if that dont work,could be a knackered remote

try programmeing the remote back into the alarm with the keypad if this doesn't work email me and will explain how to rest keys to alarm
cheers Adrian

Thanks for the replies, I've tried the batteries from the working remote and still no joy. I've had subaru try and re programme the key to the system without success. Have now requested a new fob under warranty.

Thankyou for your help.