No after sales service from Land Rover Centurion

I bought a second-hand Land Rover Defender from the Centurion branch. The car is still under the full Land Rover maintenance plan, the light for coolant level low (red light) went on the first week after I bought it. According to me and other experts this will be picked up by the computer and when the workshop take the car in it will show on the details. I took the car In and was told that it is something faulty on the coolant bottel or holder and that they will replace it. After 2 days and no feedback I was told to pick the car up without any replacement and that they can't solve the problem. It is now nearly 4 months later and I have decided to give this one to my friends in the media as it keeps on happening and it is just not acceptable that I as a client should be fine with this. I am sad and disappointed as I have been driving Land Rovers for the last 15 Years and this is heartbreaking as I know another article will do allot of damage to one of my favourite brands.