After many weeks of having a car sitting in the car park stricken with the dreaded immobiliser problem, I now have a car which moves under its' own steam.
I tried all the free fixes I could find ( I refused to pay the £120 the local Renault garage wanted to turn the immobiliser off and the £60 it would cost to get the car there & back, (Tax & MOT out its been that long!))
Thanks to links on this site I got the bypass code for the immobilser - you need the chasis & engine no. and the no. found inside the key on the little circuit board, and a program found inlinks on this site. (v. helpfull)
Problem was I couldn't find a way to put the code into the car! Central locking button method doesn't work on my car for some reason (1999 laguna 1.9dci) nor does the throttle/wiper stalk method - no button on the end of the stalk. Found a mention of disconnecting the battery - apparently resets the immobiliser. Tried this, leaving it overnight. Reconnected the battery next day, turned the key in the ignition, the little light on the dashboard stopped flashing and SUCCESS, it started! Twice to be exact but then wouldn't start again, damned immobiliser light flashing - those of you who have had this problem know what I mean. Disconnected the battery again and left it for a couple of days and tried again. There was a definite click when the the battery was reconnected and tried to start the car again. That was 8 hours ago and so far so good. It has started at every turn of the key - I've tried it about 20 times through out the day.
I hope this helps anyone else with a similar problem.
It may be pure luck but I don't care, I have a car which goes!