Rover 25 Low Engine Coolant light staying on ( we need your help)?

I have recently purchased a 25 for my wife its the GLI model on a 55 plate its had strange electrical faults such as inoperable horn, irregular security alarm sounding, strange fault with locking system off key fob, a faulty electric sunroof which tilts but wont slide, and a suspected broken electric window mechanism on the drivers side. All not a problem except the horn for its next MOT. However today when she started it the instrument panel shows a Low Engine Coolant light on and staying on. It has a full coolant system and anti freeze, I sqeezed all the pipes to try dislodge any air. I've checked the oil and its good to go? I'm stumped the car seems to be running absolutely fine no idle issues no heat or cold issues! so please if you know these engines we could use your help

Steve
February 2012