Hi, I guess Lisa sorted this out or I hope so anyway.
I have a similar problem and I hope you don't mind me posting it here rather than make a new thread.
I have a Clio P reg with an older style immobilser, no remote or even central locking.
Same problem, one day it will play up and then it is fine for a month and then it does it again. Well for the past year and a half its been fine but I had to get the RAC out on Friday because it was back again.
The thing is, my keys don't have batteries and the problem occurs with both keys so it must be the receiver. However, I don't think my receiver is in the roof, i think it is by the ignition.
Any ideas? All the other post I can find are for people with posh remote locking
You see, it works today and will probably work tomorrow morning so do I drive to work and risk getting stranded there again?