Hello, new to this forum

The wife's mother gave me her old Clio a few months ago as she had bought a new car. It is a V plate 1.4 Clio 4 door. The first thing I discovered was that the offside rear passenger door was permanently locked and whatever I did made no difference. I have removed the door card ( not all that easy with the door shut!) but I cannot see a way of releasing the door lock mechanism. I have read in places "keep poking around with a screwdriver and eventually it will open" I have tried this for hours and not got anywhere. I know this is a common problem with Clios. Any advice? The second thing that happened is the car now refuses to start at all. Battery fully charged, all lights come on when key turned but when you turn it further to start, nothing, not even a click. Battery terminals checked and earth strap. Somebody suggested it could be a problem with the immobiliser or needs a new start motor. Is the any way to check the immobiliser is working OK