i know it seems crazy.... but my central locking/ alarm is doing the same (intermitently ) it is a 53 plate gen 3 though. there are a few posts on here from peeps alarms/ locking acting up at the mo. the u.k must be the twighlight zone for coupe's lately.
sometimes won't arm/ disarm the alarm or lock/unlock the doors, yet its working fine by locking it manually with the key.
mine is going into the dealer's at warrington on saturday, they can p*ss around with it, being under warranty.
im going to make so much noise, they should hopefully replace the alarm unit. i hope ?? its too much agro for me to be back an forth to the dealers, just never have the time, so i hope it gets sorted once an for all.
neil