renault clio Dynamique 03?

Hi, thank god i have found you all. I bought an 03 plate clio 6 months ago and since the cold weather came i have had intermittent problems with the immobiliser. Sometimes the car will start other times it has none of it. I've called out the AA five times in the past two months. The AA man said only Renault can fix it so i am booked in tomorrow morning for a £90 diagnostics test. But from what I have read should i go ahead? I went onto remotekey and they only deal with up to the year 2000 models. Can anyone suggest what to do next? I don't even know where the immboliser is in the car, but it does have a sunroof.